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UNIVERSITY    OF    ILLINOIS    LIBRARY    AT    URBANA-CHAMPAIGN 


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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  No.  255 


CORN   ROOT,  STALK,  AND   EAR   ROT   DISEASES, 

AND  THEIR  CONTROL  THRU  SEED 

SELECTION  AND  BREEDING 

IN  COOPERATION  WITH  OFFICE  OF  CEREAL  INVESTIGATIONS 
BUREAU  OF  PLANT  INDUSTRY,  U.  S.  DEPARTMENT  OF  AGRICULTURE 


BY  JAMES  E.  HOLBERT,  W.  L.  BURLISON, 

BENJAMIN  KOEHLER,  C.  M.  WOODWORTH, 

AND  GEORGE  H.  DUNCAN 


URBANA,  ILLINOIS,  AUGUST,  1924 


CONTENTS 

INTRODUCTION 239 

I.  REVIEW  OF  LITERATURE  ON  EAR  CHARACTERS  OF  CORN  AS 

RELATED  TO  YIELD 240 

II.  CAUSES  AND  SYMPTOMS  OF  CORN  ROT   DISEASES 243 

PARASITIC  FACTORS 245 

Scutellum  Rot 245 

Diplodia  Root  Rot,  Ear  Rot,  and  Seedling  Blight 251 

Fusarium  Root  Rot  and  Ear  Rot 265 

Black-Bundle  Disease  269 

Miscellaneous  Ear  Rots  and  Molds 271 

Bacterial  Wilt  (Stewart's  Disease) 272 

Gibberella  Root  Rot,  Ear  Rot,  and  Seedling  Blight  of  Corn 274 

Corn  Smut  279 

Miscellaneous  Soil  Borne  Diseases 281 

Corn  Rust  and  Other  Diseases 282 

ENVIRONMENTAL  FACTORS  283 

Soil  Temperature  and  Time  of  Planting 283 

Soil  Moisture  a  Highly  Important  Factor 304 

Influence  of  Soil  Aeration . . .  . 307 

Effect  of  Amount  of  Plant-Food  Materials  in  Soil  Solution 309 

Injurious  Constituents  in  Soil  Solution 319 

Influence  of  Crop  Sequence 323 

GENETIC  FACTORS 328 

III.  ECONOMIC  IMPORTANCE  OF  CORN  ROT  DISEASES 346 

FIELD  EXPERIMENTS  WITH  VARIOUS  SEED  SELECTIONS.  .346 

Scutellum-Rotted  Seed 346 

Diplodia-Inf ected  Seed  347 

Fusarium-Inf ected  Seed 347 

Cephalosporium-Inf ected  Seed 351 

EXTENT  OF  SEED  INFECTION  ON  ILLINOIS  FARMS 353 

ESTIMATE  OF  LOSSES  DUE  TO  CORN  DISEASES 353 

IV.  EXPERIMENTAL  CONDITIONS  AND  METHODS 354 

EXPERIMENTAL  PLOTS 354 

STRAINS  OF  CORN  USED 356 

GERMINATION  AND  SELECTION  OF  SEED 357 

PLANTING  AND  CULTURAL  METHODS 360 

HARVESTING  METHODS    362 

STATISTICAL  ANALYSIS 363 

V.  PHYSICAL  CHARACTERS  OF   SEED   EARS  ASSOCIATED  WITH 

SEED  INFECTION  AND   NON-INFECTION 366 

EARLY  WORK  ON   THE   GERMINATOR   TO   DETECT   NON-IN- 
FECTION AND  SUPERIOR  VIGOR 366 

RELATION  OF  GENERAL   APPEARANCE   OF   SEED   EARS  TO 
SEED  CONDITION  .  . .  368 


Luster  of  £ar *.>>.* 369 

Shank  Attachment  369 

Ear-Tip  Covering 371 

Kernel  Indentation   373 

Nature  of  Endosperm 373 

Luster  of  Kernel 376 

General  Discussion 376 

VALUE  OF  SINGLE  EAE  CHARACTERS  IN  SEED  SELECTION.  .382 

Shank  Attachment   382 

Nature  of  Endosperm 386 

Luster  of  Kernel 389 

VI.  SUSCEPTIBILITY  AND    RESISTANCE    TO    THE    ROOT,  STALK, 

AND  EAR  ROT  DISEASES 393 

EVIDENCES  OF  SUSCEPTIBILITY  AND  RESISTANCE 393 

Influence  of  Healthy  and  of  Diseased  Parent  Plants 393 

Influence  of  Character  of  Endosperm 403 

Differences  in  Commercial   Strains 406 

PHYSICAL  CHARACTERS  OF  SEED  CORN  ASSOCIATED  WITH 

SUSCEPTIBILITY  AND  RESISTANCE 411 

VALUE   OF   PHYSICAL   APPEARANCE   AS   A   BASIS   FOR   SE- 
LECTION   431 

VII.  A  PROGRAM  OF  CORN  IMPROVEMENT 447 

TWO  METHODS  OF  IMPROVING  CORN 447 

THE  SELECTION  METHOD 448 

THE  PURE-LINE  METHOD. 455 

PROBABLE    USES    OF    THE    TWO    METHODS    OF    CORN    IM- 
PROVEMENT   469 

SUMMARY   470 

LITERATURE  CITED 472 


CORN  ROOT,  STALK,  AND   EAR   ROT   DISEASES, 

AND  THEIR  CONTROL  THRU  SEED 

SELECTION  AND  BREEDING 

BY  JAMES  E.  HOLBERT,  W.  L.  BURLISON,  BENJAMIN  KOEHLER, 

C.    M.   WOODWORTH,   AND   GEORGE   H.   DUNGAN1 

INTRODUCTION 

The  relation  that  stalk,  ear,  and  kernel  characters  of  corn  bear 
to  yield  has  been  given  much  attention  by  plant  breeders  and  agrono- 
mists. Kecently  the  relation  which  the  physical  characters  of  the 
mother  plant  and  seed  ear  may  bear  to  disease  resistance  in  the 
progeny  has  appeared  as  one  of  the  most  important  problems  of 
the  corn  breeder. 

The  actual  losses  caused  by  corn  diseases  in  the  corn  belt  states 
cannot  be  accurately  estimated.  If  it  were  possible  to  determine  the 
losses  caused  by  poor  stands  resulting  from  the  planting  of  infected 
seed  and  also  the  losses  due  to  the  stunting  of  the  growth  of  the 
many  remaining  plants,  with  the  consequent  reduction  in  size  of  ears, 
it  is  believed  that  the  total  would  be  fully  10  percent  and  perhaps 
more.  Losses  varying  from  5  to  50  percent  have  been  observed  by 
the  authors. 

The  breeding  and  multiplication  of  productive  strains  and  varie- 
ties of  corn  highly  resistant  to  disease  and  to  injury  from  unfavorable 
soil  and  weather  conditions  is  recognized  as  a  problem  demanding 
the  attention  and  active  cooperation  of  experiment  station  workers, 
corn  breeders,  and  corn  growers.  Several  years  of  experimental  work 
bearing  on  various  angles  of  the  subject  are  reported  in  the  present 
bulletin.  A  glance  at  the  table  of  contents  will  show  the  scope  of 
the  work.  The  summary  on  pages  470  and  471  states  briefly  the  out- 
standing facts  of  the  study. 


1  JAMES  R.  HOLBERT,  Agronomist,  Office  of  Cereal  Investigations,  Bureau  of 
Plant  Industry,  United  States  Department  of  Agriculture;  W.  L.  BURLISON,  Head  of 
Department  of  Agronomy  and  Chief  in  Crop  Production,  Illinois  Agricultural  Experiment 
Station;  BENJAMIN  KOEHLER,  Assistant  Pathologist,  Office  of  Cereal  Investigations, 
Bureau  of  Plant  Industry,  United  States  Department  of  Agriculture;  C.  M.  WOOD- 
WORTH,  Associate  Chief  in  charge  of  Plant  Breeding,  Illinois  Agricultural  Experiment 
Station;  GEORGE  H.  DUNGAN,  Associate  in  Crop  Production,  Illinois  Agricultural 
Experiment  Station. 

The  authors  wish  to  express  their  appreciation  to  Dr.  Carlton  R.  Ball,  Dr.  H.  B. 
Humphrey,  Dr.  A.  G.  Johnson,  and  Mr.  Eugene  Funk  for  encouragement  and  assistance 
thruout  the  investigations  reported  in  this  bulletin. 

239 


240  BULLETIN   No.   255  [August, 

PART  I 

REVIEW  OF  LITERATURE  ON   EAR  CHARACTERS  OF 
CORN  AS  RELATED  TO  YIELD 

The  results  of  investigations  on  ear  characters  of  corn  in  rela- 
tion to  yield  are  conflicting,  as  will  be  noted  from  the  following  re- 
view of  the  literature  on  this  subject. 

Montgomery72  seems  to  favor  the  long  smooth  type  of  seed  ear.  He 
found  that  extra  large  ears  gave  no  better  yields  than  ears  of  medium 
size.  Hartley36  found  no  positive  relationship  between  ear  characters 
and  yield.  Ewing26  studied  many  stalk  characters  in  relation  to  yield, 
but  observed  that  "in  most  cases  the  coefficient  of  correlation  is  so 
small  that  it  is  probably  not  worth  while  to  try  to  classify  it  o>r  even 
to  conclude  that  there  is  a  correlation. ' '  Love63  feels  that  one  of  the 
very  important  questions  arising  in  the  improvement  of  corn  is  the 
extent  to  which  visible  seed  ear  characters  are  correlated  with  yield. 
Prom  his  study  to  determine  whether  there  are  certain  characters 
indicative  of  high  yield  which  should  be  kept  in  mind  when  seed  is 
being  selected,  he  states: 

"There  is  evidently  some  effect  of  size  of  ear,  both  in  respect  to  length 
and  weight,  on  the  yield  of  the  offspring.  On  the  other  hand,  such  char- 
acters as  number  of  rows,  average  weight  of  kernel,  and  ratio  of  tip  to  butt 
do  not  have  any  very  marked  effect  on  yield. ' ' 

Funk27  has  long  maintained  that  ears  with  medium  smooth  indenta- 
tion, or  medium  smooth  ears,  will  outyield  rough  starchy  ones. 

Sconce88  began  systematic  corn  breeding  in  1905  in  an  attempt  to 
determine  some  of  the  principles  of  corn  improvement.  His  first  study 
was  the  relation  which  the  number  of  rows  of  kernels  and  the  shape 
of  the  kernels  bear  to  yield.  He  found  that  ears  with  twenty  rows 
stood  slightly  higher  in  yield  than  ears  with  a  larger  or  a  smaller 
number.  He  further  states  that — 

"a  kernel  of  medium  depth  with  a  large  amount  of  horny  material  will  on 
the  average  give  the  highest  yield,  and  that  the  yield  of  an  ear  of  corn 
having  a  long,  rough,  narrow  kernel  containing  a  large  amount  of  starch 
will  not  compare  at  all  favorably  with  that  of  an  ear  having  a  kernel  of 
medium  length  and  a  well  rounded  tip." 

McCall  and  Wheeler66  found  no  correlation  between  "length, 
weight,  circumference,  and  density"  of  the  ear  of  corn  and  yield. 
Williams  and  Welton,115  who  have  reported  very  completely  on  the 
relation  of  ear  characters  to  yield,  find  no  significant  relation  between 
these  two  factors.  Cunningham14  studied  very  carefully  certain 
physical  characters,  such  as  length  of  ear,  circumference  of  ear,  filling 
of  tips,  rounding  of  butts,  indentation  of  kernels,  and  percentage  of 
grain  to  cob  in  relation  to  yield.  His  comments  are  as  follows: 


1924}  CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES  241 

' '  The  data  available  indicate  that  certain  ear  characters  have  been  given 
more  consideration  than  their  worth  as  related  to  yield  warrants,  while 
other  characters  have  been  emphasized  that  may  actually  tend  to  decrease 
yield.  ...  It  is  a  well  known  fact  that  under  Kansas  conditions  com- 
paratively smooth  types  of  com  produce  better  under  adverse  conditions 
than  the  roughly  indented  types." 

In  a  later  publication  he15  stated : 

"Every  corn  grower  knows  that  the  smooth  type  is  much  to  be  pre- 
ferred at  husking  time.  This  type  is  not  so  subject  to  damage  from  molds 
and  other  fungi  following  injury  to  the  ears  from  the  corn  ear  worm." 

Love  and  Wentz65  found  that— 

' '  The  characters  of  length,  ratio  of  tip  circumference  to  butt  circumference, 
average  circumference  of  cob,  weight,  average  weight  of  kernels,  number 
of  rows  of  kernels,  and  average  length  and  width  of  kernels  on  the  seed 
ears  do  not  show  correlation  significant  enough  to  be  of  value  in  judging 
seed  corn."  There  seems  to  be  a  negative  correlation  between  percentage 
of  grain  in  the  seed  ear  and  yield.  Circumference  of  the  seed  ear  has 
some  significance. 

Hughes,51  reporting  on  preliminary  trials  with  prize-winning  samples 
of  corn,  states  that  the  highest-scoring  samples  gave  the  highest  yields 
by  about  five  bushels  per  acre. 

The  data  of  Hutcheson  and  Wolf52  show  certain  relations  between 
ear  characters  and  yield.  They  state  that  there  is  some  significance 
in  the  relation  of  length,  circumference,  uniformity  of  type,  and 
shape  of  ears  to  yield.  Emphasis  is  placed  on  the  fact  that  "high- 
yielding  strains  of  corn  are  high-scoring  strains." 

Biggar5  studied  the  relation  between  yield  and  certain  ear  char- 
acters, such  as  weight  and  length  of  ears,  number  of  rows,  and  shelling 
percentage.  He  concludes  that : 

"There  seems  to  be  no  special  relation  between  number  of  rows  and 
yield  or  between  shelling  percentage  and  yield.  The  characters  of  length 
and  weight  of  ears  show  positive  correlation  with  yield,  but  they  are  not 
consistently  large.  The  character  of  length  seems  to  be  somewhat  sig- 
nificant, at  least  for  some  of  the  varieties.  The  results  on  the  whole  would 
indicate  that  there  is  no  well  marked  basis  for  using  ear  characters  to 
indicate  yield  possibilities." 

Pearl  and  Surface76  found  no  significant  relation  in  "size  or  con- 
formation" of  seed  ears  of  sweet  corn  and  yield. 

Olson,  Bull,  and  Hays74  have  given  careful  consideration  to  the 
question  of  ear  characters  as  a  basis  on  which  to  select  seed  corn  ears. 
Their  data — 

"offer  no  encouragement  for  selection  emphasizing  length  in  the  hope  of 
obtaining  important  increases  in  yield."  In  the  matter  of  the  relation  of 
weight  to  yield  it  is  suggested  that  any  conscious  selection  for  weight  of 
ears  should  consist  simply  of  elimination  of  extremes.  "In  fact  one  is 


242  BULLETIN   No.   255  [August, 

probably  safe  in  picking  at  random  so  far  as  weight  is  concerned."  The 
relation  of  shelling  percentage  to  yield  "  indicates  no  advantage  in  selecting 
seed  ears  of  extremely  high-shelling  percentage,  but  a  slight  advantage  in 
eliminating  those  of  very  low-shelling  percentage." 

These  same  investigators  state  that  the  relation  shown  between  ear 
circumference  and  yield  was  apparently  inverse.  The  differences  in 
yield  between  the  ears  of  different  circumferences  were  so  small  as  to 
be  practically  negligible.  In  the  tests  on  the  relation  of  character  of 
butts  to  yield,  they  found  that  possibly  a  slight  negative  correlation 
existed.  A  slight  negative  correlation  was  also  found  in  a  general  way 
between  character  of  tips  and  yield.  In  the  matter  of  kernel  uni- 
formity these  same  investigators  felt  that  possibly  some  negative  re- 
lation to  yield  exists. 

Manns  and  Adams68  have  found  that  ''Ears  having  smooth, 
properly  dented  kernels,  somewhat  flinty,  make  better  seed  and  are 
freer  from  disease  than  the  rough  ears,  which  are  usually  very 
starchy."  Valleau109  found  that  "selection  for  the  e'xtremes  of  smooth 
ears  and  rough  ears  .  .  .  resulted  in  increases  of  39.4  and  13.9  per- 
cent in  yield  for  the  smooth  type  over  the  rough."  Kiesselbach58 
concludes  that  ' ' it  will  be  found  that  the  sound  seed  occurs  in  rather 
slender,  solid,  hard,  smooth,  flinty  ears  with  kernels  of  only  medium 
depth." 


CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES  243 


PART  II 

CAUSES  AND  SYMPTOMS  OF  CORN  ROT  DISEASES 

The  corn  root,  stalk,  and  ear  rot  diseases  are  a  group  of  diseases 
seriously  affecting  the  corn  crop.  For  brevity,  these  diseases  are  some- 
times called  "corn  rot  diseases,"  and  frequently  simply  ''corn  root 
rot."  However,  at  the  outset  it  must  be  realized  that  "corn  root  rot" 
is  not  one  disease,  but  several  diseases,  some  of  which  do  not  result 
in  any  rotting  of  either  roots  or  stalks.  In  general,  most  of  these 
diseases  cause  a  reduction  in  field  stand,  a  reduction  in  health  and 
vigor  of  surviving  plants,  and  a  reduction  in  both  yield  and  quality 
of  grain.  They  may  cause  a  chlorosis,  or  yellowing  of  the  leaves,  de- 
layed silking  and  pollination,  firing  and  a  general  blighting  of  the 
plants,  lodging,  barrenness,  and  nubbin  production  in  various  forms. 

Not  all  the  rot  diseases  of  corn  can  be  traced  to  the  same  type  of 
causative  agent.  In  general,  the  corn  rot  diseases  herein  described 
and  discussed  are  due  to  a  combination  of  causes  brought  about  thru 
the  interrelation  of  parasitic  organisms  with  unfavorable  environment 
and  inferior  genetic  constitution  of  the  host.  Other  disorders  of  the 
corn  plant  which  are  somewhat  similar  in  above-ground  symptoms  are 
primarily  the  result  of  a  lack  of  proper  nutrient  elements  in  the  soil, 
the  physiological  balance  thus  being  deranged.  Some  strains  of  corn, 
on  account  of  their  genetic  constitution,  have  a  very  narrow  range 
of  adaptability  and  are  able  to  yield  satisfactorily  only  under  the 
most  favorable  environment,  a  condition  that  frequently  does  not  ob- 
tain in  actual  field  practice.  However,  there  is  considerable  inter- 
action of  causative  agencies,  and  any  grouping  of  these  agencies  must 
necessarily  be  more  or  less  general.  This  close  interaction  may  be 
illustrated  by  reference  to  some  of  the  known  facts  concerning  the 
relation  of  one  of  the  parasites  of  corn  to  the  development  of  seedling 
blight. 

Gibberella  saubinetii  (Mont)  Sacc..  the  wheat  scab  organism,  may 
cause  seedling  blight  of  corn  and  a  reduction  in  early  vigor  and  gen- 
eral health  of  the  corn  plant.46'18-19  Dickson,18- 19  of  the  Wisconsin 
Agricultural  Experiment  Station  and  the  United  States  Department 
of  Agriculture,  has  shown  that  corn  seedlings  become  susceptible  to 
the  wheat  scab  parasite  only  when  grown  under  certain  environmental 
conditions.  He  found  that  they  were  susceptible  when  grown  in  a 
moist,  cool  soil,  below  20°  C.,  or  68°  F.,  or  when  grown  in  a  fairly  dry 
soil  at  a  much  wider  range  of  temperature.  He  states:18 

"The  results,  therefore,  indicate  that  in  this  case,  at  least,  disease  re- 
sistance and  predisposition  to  disease  may  be  largely  dependent  upon  en- 
vironmental conditions  under  which  the  plant  is  developing." 


244  BULLETIN   No.   255  [August, 

Eckerson  and  Dickson23  have  explained  the  variation  in  seedlings 
in  their  susceptibility  to  seedling  blight  as  probably  due  to  marked 
differences  in  the  chemical  composition  of  corn  seedlings  grown  under 
different  soil  temperature  and  moisture  conditions.  They  state: 

"Corn  seedlings  grown  at  high  soil  temperatures  are  high  in  available 
carbohydrates  and  low  in  available  nitrogen.  The  cell  walls,  even  in  early 
seedling  stage,  are  cellulose,  soon  impregnated  with  suberin.  Corn  seed- 
lings grown  at  low  soil  temperatures  have  little  or  no  available  carbohy- 
drates and  are  high  in  available  nitrogen.  The  cell  walls  are  composed  of 
pectic  materials,  cellulose  being  absent  until  after  photosynthesis  begins. 
.  .  .  The  parasite  penetrates  the  walls  of  pectic  materials  apparently 
with  little  resistance,  whereas  it  penetrates  the  cellulose  walls  slowly.  .  .  . 
These  differences  apparently  explain  the  variation  in  their  susceptibility 
to  seedling  blight  produced  by  Gibbcrella  saubinetii." 

Later  Dickson,  Eckerson,  and  Link20  made  the  following  addi- 
tional statement: 

"Because  of  an  abundance  of  sugar  and  fat  available  in  the  corn  em- 
bryos at  high  temperatures,  a  carbohydrate  reserve  Exists  for  building 
thicker,  more  resistant  cell  walls. ' ' 

Data  presented  later  in  this  bulletin  and  also  data  by  Koehler, 
Dickson,  and  Holbert60  show  that  one  selection  of  yellow  dent  corn 
may  be  very  susceptible  to  this  parasite  while  another  selection  of 
the  same  strain  grown  under  the  same  environmental  conditions  may 
be  highly  resistant.  In  such  cases  the  genetic  constitution  of  the  corn 
apparently  was  more  important  than  environmental  factors  in  in- 
fluencing resistance  and  susceptibility  to  this  parasite. 

The  findings  of  Dickson19  and  of  Eckerson  and  Dickson23  conflict 
in  no  way  with  the  data  on  the  varying  susceptibility  of  corn  to  seed- 
ling blight  reported  in  this  bulletin.  Environmental  factors,  including 
soil  factors,  are  important  in  influencing  predisposition  to  disease,  but 
the  genetic  constitution  of  the  corn  is  equally  important.  An  ade- 
quate understanding  of  the  causes  of  the  corn  root,  stalk,  and  ear  rot 
diseases,  and  variations  in  susceptibility  of  different  strains  of  corn 
to  these  diseases  can  be  obtained  only  by  a  consideration  of  all  the 
influencing  factors. 

Altho  bacterial  wilt  (Stewart's  disease)  and  corn  smut  and  rust 
are  not  grouped  with  the  corn  root,  stalk,  and  ear  rot  diseases,  and 
have  not  been  studied  specifically  by  the  authors  of  this  bulletin,  cer- 
tain observations  have  been  made  regarding  the  occurrence  of  these 
diseases  in  plots  and  fields  affected  with  the  corn  root,  stalk,  and  ear 
rot  diseases.  Selection  and  breeding  for  disease  resistance  and  pro- 
ductiveness require  a  consideration  of  all  possible  influencing  factors, 
and  to  that  end  a  brief  discussion  of  these  diseases  also  is  included  in 
the  present  bulletin. 


CORN  ROOT,  STALE,  AND  EAR  ROT  DISEASES  245 

PARASITIC  FACTORS 

SCUTELLUM  ROT 

The  germination  test  for  corn  may  be  used  to  determine  not  only 
viability,  but  also  seedling  vigor  and  seed  infection  with  some  of  the 
organisms  that  produce  disease.  Under  conditions  that  exist  during 
the  germination  test,  the  kernels  are  subjected  to  the  attack  of  cer- 
tain molds,  among  which  RJiizopus  spp.40>  1  is  the  most  common. 
The  degree  to  which  kernels  from  different  ears  are  able  to  resist  the 


FIG.  1. — NEARLY  DISEASE-FREE  SEEDLINGS 

Note  the  sturdy  plumules,  bright  kernels,  and  large  number  of  strong, 
vigorous  roots.     (See  Plate  I.) 


FlG.    2. — SCUTELLUM-ROTTED    SEEDLINGS 

Note  the  poor  root  development  and  the  spindly  plumules  as  compared 
with  those  in  Fig.  1.  Occasionally  scutellum-rotted  seedlings  will  have  a 
healthy  appearance  and  can  be  detected  only  by  cutting  the  kernels.  (See 
Plate  I.)  Under  most  conditions,  corn  grown  from  scutellum-rotted  seed 
has  produced  less  both  in  total  yield  and  in  yield  of  sound  grain  than  corn 
grown  from  good  seed. 


246 


BULLETIN   No.   255 


[August, 


growth  of  these  molds  in  the  germination  test  has  proved  to  be  a  more 
or  less  accurate  index  to  the  field  performance  of  corn  grown  from 
their  respective  ears.  Corn  grown  from  ears  which  on  the  germinator 
were  badly  affected  with  scutellum  rot  (see  description  in  legends  of 
colored  Plate  I  and  Figs.  1  and  2),  a  condition  usually  indicated  by 
invasions  with  Rhizopus  spp.  on  the  germinator,  has  been  more  sus- 
ceptible to  attacks -of  soil  fungi  and  to  injury  from  inoculations  with 
certain  corn  parasites  than  has  corn  grown  from  ears  approximately 
the  same  in  viability  and  vigor,  but  neither  affected  with  scutellum 
rot  nor  infected  with  parasitic  organisms.  Under  most  conditions,  corn 
grown  from  scutellum-rotted  seed  has  produced  less  both  in  total  yield 
and  in  yield  of  sound  grain  than  corn  grown  from  good-  seed. 


FIG.  3. — CORN  FROM  GOOD  SEED 

This  corn  yielded  at  the  rate  of  74.7  bushels  per  acre. 
U.  S.  Department  of  Agriculture  experimental  plots  on  the 
farm  of  Mr.  E.  D.  Funk,  Bloomington.  (Compare  with  Fig.  4.) 

The  fundamental  cause  of  the  difference  in  resistance  and  sus- 
ceptibility to  Rhizopus  spp.  on  the  germinator  is  not  known,  nor  is 
the  disease-susceptibility  of  corn  grown  from  scutellum-rotted  seed 
fully  understood.  However,  this  does  not  alter  the  economic  value 
of  this  feature  of  the  germination  test  in  eliminating  ears  that  are 
likely  to  produce  corn  susceptible  to  disease. 

The  most  outstanding  difference  between  corn  grown  from  seed 
affected  on  the  germinator  with  scutellum.  rot  and  that  grown  from 
good  seed  is  the  reduction  in  early  vigor  of  the  plants  in  the  field 
(Figs.  3,  4,  and  5).  Early  vigor  and  yield  of  grain  are  closely  cor- 
related.48 Plants  that  are  weak  or  only  moderately  strong  in  their 
early  growth  are  very  likely  to  be  late  in  forming  ears  and  delayed 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


247 


FIG.  4. — CORN  FROM  SCUTELLUM -ROTTED  SEED 

This  corn  yielded  at  the  rate  of  57.7  bushels  per  acre. 
U.  S.  Department  of  Agriculture  experimental  plots  on  the 
farm  of  Mr.  E.  D.  Funk,  Bloomington.  (Compare  with  Fig.  3.) 


FIG.  5. — CORN  FROM  SCUTELLUM -ROTTED  SEED  (LEFT)  AND  FROM  GOOD  SEED 
OF  THE  SAME  STRAIN  (RIGHT) 

An  experiment  conducted  in  1921  on  the  farm  of  Mr.  Claude  Thorpe, 
De  Witt  county,  the  U.  S.  Department  of  Agriculture  and  the  Illinois 
Agricultural  Experiment  Station  cooperating.  The  outstanding  difference 
between  corn  grown  from  seed  affected  on  the  germinator  with  scutellum 
rot  and  that  grown  from  good  seed  is  the  reduction  in  early  vigor  of  the 
plants  in  the  field. 


248 


BULLETIN  No.   255 


[August, 


in  maturity.  If  they  are  decidedly  weak  in  their  early  growth,  they 
probably  will  be  barren  or  produce  nubbins  only.  Thus  corn  from 
scutellum-rotted  seed  usually  is  inferior  to  corn  from  good  seed  in 


FIG.  6. — CORN  FROM  GOOD  SEED 

Corn  grown  on  a  U.  S.  Department  of  Agriculture 
experimental  plot  on  the  farm  of  Mr.  Claire  Golden,  Rock 
Island  county.  (Compare  with  Fig.  7.) 


1924] 


CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES 


249 


both  total  yield  and  quality  of  grain.  Occasionally  the  contrast  at 
harvest  between  corn  grown  from,  good  seed  and  that  grown  from 
scutellum-rotted  seed  is  very  marked  (Figs.  6  and  7). 


FIG.  7. — CORN  FROM  SCUTELLUM-ROTTED  SEED 

The  seed  from  which  this  corn  was  grown  showed  a 
high  percentage  of  scutellum  rot  on  the  germinator. 
(Compare  with  Fig.  6.)  Occasionally  the  contrast  at 
harvest  time  between  corn  grown  from  good  seed  and  that 
grown  from  scutellum-rotted  seed  is  very  marked. 


PLATE  I 

t< 

A,  B         Vigorous  disease-free  seedlings. 

Note  the  clean,  healthy  appearance  of  both  exterior  and  interior,  as 
well  as  the  large  number  of  strong  roots.  The  germination  test  is  a 
valuable  means  of  selecting  seed  with  superior  vigor. 

C,  D         Fusarium-infected   seedlings. 

The  pink-colored  fungus  growth  on  the  exterior  of  the  kernels  is  very 
characteristic  of  Fusarium-infected  seedlings. 

E,  G         Scutellum-rotted  seedlings  with  no  conspicious  mycelial  growth  on  the 

exterior  of  the  kernels. 

F,  H         Scutellum-rotted   seedlings   with   Rhizopus   growing   on   the   exterior   of 

the  kernels. 

Note  the  rotted  region  (GH)  between  the  endosperm  and  the  embryo 
portion  of  the  kernel. 


250 


Corn  Root,  Stalk,  and  Ear  Rot  Diseases 


Plate  I 


Illinois  Agricultural  Experiment  Station 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


251 


DIPLODIA  ROOT  ROT,  EAR  ROT,  AND  SEEDLING  BLIGHT 

Diplodia  zeae  (Schw.)  Lev.  has  been  recognized  for  several  years 
as  an  important  parasite  of  corn.  In  1909  Burrill  and  Barrett10 
found  that  a  large  proportion  of  the  loss  from  ear  rots  was  caused  by 
this  organism.  Other  workers37- 10,  94,  25,  oe,  90,  n  ajso  have  called  atten- 
tion to  this  parasite  from  time  to  time.  Melhus  and  Durrell71  re- 
ported a  widespread  Diplodia  infection  of  seed  in  eastern  and  central 


FlG.    8. — DlPLODIA-lNFECTED    SEEDLINGS 

Diplodia-infected  seed  can  best  be  detected  by  the  use  of  the  germina- 
tion test.     (See  Plate  II.) 


FIG.  9. — CORN  FROM  DIPLODIA-INFECTED  SEED  (LEFT)  AND  FROM  GOOD  SEED 
OF  THE  SAME  STRAIN  (BIGHT),  UNIVERSITY  SOUTH  FARM,  URBANA 

Seed  apparently  good  but  infected  with  this  organism  results  in  a  re- 
duced field  stand  under  most  conditions. 


PLATE  II 

A,  B        Vigorous,  disease-free  seedlings. 
C-H  Diplodia-infected  seedlings  and  kernel  (F). 

The  germination  test  is  a  valuable  aid  in  detecting  Diplodia-infected  seed. 

Diplodia  seae  develops  abundantly  on  infected  kernels  in  a  germination 
test  and  causes  decay  of  the  shoots  in  the  region  near  the  kernel.  In 
advanced  stages  the  fungus  itself  appears  as  a  dense,  white  mold  cover- 
ing part  of  the  kernel. 


252 


Corn  Root,  Stalk,  and  Ear  Rot  Diseases 


Plate  II 


Illinois  Agricultural  Experiment  Station 


CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES 


253 


Iowa  as  a  result  of  excessive  rainfall  accompanied  by  hot  weather  in 
the  fall  of  1921. 

Diplodia  zeae  develops  abundantly  on  infected  kernels  in  a  germi- 
nation test  and  causes  a  decay  of  the  shoots  in  the  region  near  the 
kernel  (Fig.  8  and  Plate  II).  In  advanced  stages,  the  fungus  itself 
appears  as  a  dense,  white  mold  covering  part  of  the  kernel.  The 
mycelial  growth  is  seldom  conspicuous  on  rotted  roots  and  shoots  ex- 
cept near  decayed  areas. 

The  planting  of  seed  which  is  apparently  good  but  infected  with 
this  organism  results  in  a  reduced  field  stand  under  most  conditions 
(Fig.  9).  Surviving  plants  usually  make  a  very  irregular  growth, 
depending  on  the  severity  of  infection,  the  resistance  of  the  individual 
plant  attacked,  and  environmental  factors  (Figs.  10  to  14).  Many 
weak  plants  (Fig.  15)  infected  with  this  parasite  wilt  and  die  during 
the  season  as  a  result  of  the  rotting  of  the  roots  near  the  crown. 
Other  infected  plants  may  neither  be  blighted  nor  die,  the  principal 
above-ground  symptoms  in  such  cases  being  a  marked  reduction  in 
vigor  and  in  the  height  of  plants  (Table  1  and  Fig.  16).  The  meso- 
cotyls  of  young  corn  plants  grown  from  Diplodia-infected  seed  usually 
appear  dry  and  brown  in  contrast  to  the  white,  healthy  appearance 
of  mesocotyls  of  plants  of  the  same  age  grown  from  good  seed  (Plate 
III).  There  is  little  evidence  that  this  fungus  advances  up  the  stalk 
from  the  rotted  roots  and  rotted  crown. 

TABLE  1. — REDUCTION  IN  HEIGHT  OF  CORN  PLANTS  GROWN  FROM  DIPLODIA- 
INFECTED  SEED 
Ontario  Parish,  near  Oneida,  1923 


Number  of 

Mean  plant  height 

Reduction 

Soil 
treatment 

Age 

plants 
measured 
in  each  plot 

Nearly 
disease- 
free  seed 

Diplodia- 
infected 
seed 

Reduction 

Probable 
error 

days 

inches 

inches 

inches 

None  

17 

25 

9.3  +  0.20 

7.8  +  0.23 

1.5  +  0.30 

5.0 

17 

25 

9.3  +  0.22 

7.7  +  0.15 

1.6  +  0.27 

5.9 

17 

25 

9.1  +  0.30 

7.5  +  0.22 

1.6  +  0.37 

4.3 

32 

25 

16.0  +  0.52 

15.0  +  0.86 

1.0  +  1.00 

1.0 

32 

25 

15.5  +  0.47 

13.2  +  0.60 

2.3  +  0.76 

3.0 

42 

25 

17.6  +  0.65 

15.5  +  0.47 

2.1  +  0.80 

2.6 

42 

25 

20.9  +  0.87 

17.6  ±  0.68 

3.3  +  1.10 

3.3 

Lime     

17 

25 

10.5  +  0.16 

7.7  +  0.25 

2.8  +  0.30 

9.3 

32 

25 

19.4  +  0.47 

12.3  +  0.78 

7.1  +  0.91 

7.8 

42 

25 

21.5  ±  0.55 

17.6  ±  0.80 

3.9  ±  0.97 

4.0 

Phosphate  . 

17 
32 

25 
25 

11.3  +  0.26 
23.6  +  0.43 

8.2  +  0.23 
14.7  +  0.69 

3.1  +  0.35 
8.9  +  0.81 

8.9 
11  0 

42 

25 

24.2  ±  0.42 

18.4  ±  0.80 

5.8  ±  0.90 

6.4 

Lime  and 

17 

25 

11.7  +  0.26 

9.0  +  0.20 

2.7  4-  0.33 

8.2 

phosphate 

32 

25 

26.2  +  0.69 

17.7  +  0.72 

8.5  +  1.00 

8.5 

42 

25 

27.9  +  0.45 

20.3  +  0.79 

7.6  ±  0.91 

8.4 

254 


BULLETIN  No.   255 


[August, 


Koehler,  Dungan,  and  Holbert61  have  found  in  experimental  work 
that  frequently  more  leaning  and  down  stalks  occur  in  corn  grown 
from  seed  infected  with  Diplodia  than  in  corn  grown  from  good  seed. 
However,  in  these  same  Diplodia-infected  plots  there  was  no  signifi- 
cant increase  in  the  number  of  broken  stalks.  Data  presented  in  Table 
2  and  Chart  1  show  that  corn  grown  from  Diplodia-infected  seed  may 
have  less  resistance  to  a  vertical  pull  than  corn  grown  from  good  seed. 


Mean  pul/incf  resistance  per  ptant  f/bs) 
200  300 


400 


CHART  1. — EFFECT  OF 
DIPLODIA  INFECTION 
ON  PLANT  ANCHOR- 
AGE 

Corn  from  good  seed 
is  better  anchored, 
and  is  less  likely  to 
lodge  than  corn  from 
Diplodia-infected  seed 
(Table  2). 


In  addition  to  being  carried  over  the  winter  as  dormant  mycelium 
in  the  seed,  Diplodia  zeae  overwinters  in  diseased  corn  roots  and  stalks 
and  diseased  shanks  and  husks,  and  also  in  rotted  ears  left  in  the  field. 
The  following  statements  made  by  Burrill  and  Barrett10  in  1909  are 
still  pertinent: 

"The  first  indication  of  the  Diplodia  fungus  on  the  dead  stalks  is  the 
appearance  of  very  small  dark  colored  specks  under  the  rind.  In  outdoor 
conditions  these  may  appear  during  late  fall  and  winter,  but  usually  de- 
velop during  the  spring  and  summer.  [Fig.  17  of  this  bulletin].  .  .  . 
During  the  summer  the  necks  of  the  pycnidia  begin  to  break  thru  the  rind 
of  the  stalks  and  in  favorable  weather  conditions  send  out  large  numbers 
of  spores.  Pieces  of  diseased  stalks  one  or  two  years  old  bave  been  found 
in  July,  August,  and  September  almost  covered  with  black  tendrils  of 
spores  capable  of  quick  germination.  .  .  .  Pieces  of  stalks  almost  three 
years  old  have  been  found  bearing  pycnidia  and  some  few  of  the  spores 
found  in  them  were  capable  of  germination.  These  were  pretty  badly 
decayed,  however,  and  the  fungus  was  not  in  a  very  active  condition." 

Spores  of  this  parasite  are  picked  up  by  air  currents  during  the 
summer  and  fall  and  may  be  carried  considerable  distances.  These 


TABLE  2. — PULLING  RESISTANCE  OF  CORN  GROWN  FROM  GOOD  SEED 
AND  FROM  DIPLODIA-INFECTED  SEED 

Planted  June  14,  1923,  on  infested  brown  silt  loam  soil,  near  Bloomington, 
and  pulled  October  25-26 


Number 

Mean  pulling 

Condition  of  seed 

of 

resistance 

Difference 

Odds 

plots 

per  plant 

Good  

13 

Ibs. 
337 

Ibs. 

Diplodia-infected  

13 

313 

24 

100:1 

1924} 


CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES 


255 


spores  lodge  in  cavities  between  the  stalk  and  sheath,  on  and  around 
the  shank,  and  on  the  tip  of  the  ear.  Under  proper  temperature  and 
moisture  conditions,  these  spores  germinate  and  frequently  infect  the 
corn  plant  thru  leaf  sheaths,  nodes,  or  ear  shanks.  Durrell22  states : 

"On  the  leaf  sheaths  the  fungus  produces  reddish  or  purplish  spots  of 
varying  size  and  shape,  appearing  after  flowering  of  the  corn  plant.  These 
lesions  may  extend  down  into  the  node  of  the  stalk  or  up  the  leaf,  killing 
or  discoloring  the  midrib." 


FIG.  10. — REDUCTION  IN  VIGOR  OF  CORN  FROM  DIPLODIA-INFECTED 

SEED 

Above,  a  hill  of  corn  grown  from  nearly  disease-free  seed. 
Below,  two  hills  of  corn  grown  from  Diplodia-infected  seed.  These 
were  all  planted  on  the  same  day,  two  kernels  close  together  in  a 
hill,  under  uniform  soil  conditions. 

Ears  may  be  infected  either  thru  the  shank  or  thru  the  tip  of 
the  ear  (Figs.  18  and  19).  When  the  infection  occurs  soon  after  the 
ears  form,  the  infected  ears  are  reduced  to  a  char-like  mass  by  the 
time  uninfected  ears  are  well  dented.  Frequently,  early  infection  of 
the  young  ear  shoots  results  in  barrenness. 


256 


BULLETIN   No.   255 


[August, 


FIG.  11. — CORN  FROM  GOOD  SEED 

This  corn  yielded  at  the  rate  of  71.0  bushels  per  acre.  U.  S.  De- 
partment of  Agriculture  experimental  plots  on  the  farm  of  Mr.  E.  D. 
Funk,  Bloomington.  (Compare  with  Fig.  12.) 


FIG.  12. — CORN  FROM  DIPLODIA-INFECTED  SEED 
This  corn  yielded  at  the  rate  of  38.1  bushels  per  acre.     U.  S.  De- 
partment of  Agriculture  experimental  plots  on  the  farm  of  Mr.  E.  D. 
Funk,  Bloomington. 


1924] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


257 


FIG.  13. — INCREASED  VIGOR  OF  DIPLODIA-INFECTED  PLANTS  IN  SOIL 
RECEIVING  LIMESTONE  AND  PHOSPHATE 

Note  the  irregular  growth  of  the  Diplodia-infected  plants  (left) 
on  the  plots  receiving  no  soil  treatment  (above)  as  compared  with 
those  on  the  plots  receiving  limestone  and  phosphate  (below).  Experi- 
mental plots  at  Ontario  Parish,  near  Oneida,  conducted  cooperatively 
by  the  U.  S.  Department  of  Agriculture,  the  Illinois  Agricultural 
Experiment  Station,  and  the  Men's  Club  of  Ontario,  a  rural  church 
organization. 


PLATE  III 

A-E  Diplodia-infected  corn  plants. 

Note  the  rotted  condition  of  the  mesocotyls  and  the  fewer  roots  on  E 
as  compared  with  G. 

F-G  Healthy  corn  plants. 

Note  the  healthy  condition  of  the  mesocotyls  and  the  large  number  of 
roots. 

The  mesocotyls  of  young  corn  plants  grown  from  diplodia-infected  seed 
usually  appear  dry  and  brown  in  contrast  to  the  white,  healthy  appear- 
ance of  mesocotyls  of  plants  of  the  same  age  grown  from  good  seed. 


258 


Plate  III 


Corn  Root,  Stalk,  and  Ear  Rot  Diseases 


M   7  ; 

(M 

Illinois  Agricultural  Experiment  Station 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


259 


FIG.  14. — INCREASED  VIGOR  OF  DIPLODIA-INFECTED  PLANTS  ON  O.EAN  SOIL 

Note  that  on  the  infested  soil  (above)  the  growth  of  the  Diplodia- 
infected  plants  (left)  is  very  irregular  as  compared  with  the  plants  from 
nearly  disease-free  seed  (right),  while  on  the  clean  soil  (below)  the  growth 
on  the  two  plots  is  apparently  the  same.  Experimental  plots  on  farms  of 
Charles  Gordon  and  C.  A.  Atwood  near  Peoria. 


260 


BULLETIN   No.   255 


[August, 


FIG.  15. — CORN  FROM  DIPLODIA-INFECTED  SEED  (LEFT)  AND  FROM 
GOOD  SEED  (RIGHT) 

These  were  planted  at  the  same  time,  three  kernels  to  each  hill 
and  photographed  July  12,  1921,  forty-seven  days  after  planting. 
Note  that  only  one  plant  in  the  hill  planted  with  Diplodia-inf  ected 
seed  has  survived  and  it  is  wilting.  This  plant  finally  grew  to 
nearly  normal  height  but  was  barren.  Many  weak  plants  infected 
with  this  pa.rasite  wilt  and  die  during  the  season  as  a  result  of  the 
rotting  of  the  roots  near  the  crown. 


1924] 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


261 


FIVE  Rons  PIANTE«  DISEASE  FREE  SEED,       FIVE  Rows  PUtnBWTRMPUMAlKCiH)  SEED. 


FIG.  16. — REDUCTION  IN  HEIGHT  OF  PLANTS  FROM  DIPLODIA-INFECTED  SEED 
Corn  grown  from  Diplodia-infected  and  from  nearly  disease-free  seed 
at  Bloomington,  1922.  The  field  stand  in  these  plots  is  unusually  good  for 
corn  grown  from  Diplodia-infected  seed.  The  soil  had  been  in  virgin 
prairie  sod  previous  to  1921,  when  it  was  planted  to  corn.  The  corn  from 
the  disease-free  seed  yielded  93.7  bushels  of  sound  corn,  while  the  corn 
from  the  Diplodia-infected  seed  yielded  72.1  bushels. 


FIG.    17. — A    DIPLODIA-INFECTED 
CORN  STALK 

An  old  corn  stalk  from  the 
previous  year's  crop,  showing 
pycnidia  of  Diplodia  seae  dis- 
charging spores  soon  after  a 
warm  rain  in  August. 


262 


BULLETIN   No.    255 


[August, 


-g 

&    a 


55 

o 

£  * 


•S  p, 

CO 
®    O) 


ft 

5 


CORN  ROOT,  STALK,  ANT>  EAR  ROT  DISEASES 


263 


In  describing  the  infection  of  the  ear  by  this  fungus,  Burrill  and 
Barrett10  say: 

"The  slender  threads  penetrate  the  young  tissues  of  the  grains,  cob,  and 
husks,  progressing  from  cell  to  cell  and  extracting  from  their  content  what- 
ever is  of  value  for  food.  After  the  ear  has  become  entirely  involved  or 
the  growth  of  the  parasite  somewhat  checked  by  the  maturing  of  the  corn, 
the  fungus  begins  to  form  its  reproductive  stage.  This  consists  of  small 
black  bodies  which  develop  in  the  husks,  cobs,  and  more  rarely  in  the  grains, 
and  which  contain  large  numbers  of  purplish  brown,  rather  slender,  two- 


FIG.  20. — INNER  HUSK  FROM  DIPLODIA-INFECTED  EAR 

In  the  fruiting  stage  of  the  Diplodia  fungus  the  pycnidia 
outline  the  position  of  the  kernels  against  the  husks. 

celled  spores,  25  by  5.2  p.  in  size.  If  the  outer  husks  of  an  ear  in  a  well 
advanced  stage  of  the  disease  are  pulled  down,  the  spore  cases,  or  pycnidia 
[Fig.  20  of  this  bulletin],  will  be  seen  as  minute  black  specks  slightly  ele- 
vated above  the  surface.  .  .  .  Diseased  ears  left  in  the  field  under  natural 
conditions  eventually  develop  numerous  pycnidia  in  the  grains,  giving  them 
a  black  appearance." 

Many  apparently  good  ears  have  been  found  infected  with  this 
organism  (Fig.  21).  Such  infection  can  best  be  detected  by  the 
germination  test.  The  appearance  of  Diplodia-infected  seedlings  on 
the  germinator  is  illustrated  and  described  in  Fig.  8  and  in  Plate  II. 


264 


BULLETIN   No.   255 


[August, 


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CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES 


265 


FUSARIUM  ROOT   ROT   AND  EAR  ROT 

Probably  the  most  common  fungus  appearing  in  the  germination 
test  of  seed  corn  is  Fusarium  moniliforme  Sheldon.  In  regard  to  this 
fungus,  Sherbakoff,92  of  the  Tennessee  Agricultural  Experiment  Sta- 
tion, makes  the  following  statements : 

"Among  the  Fusaria  answering  Sheldon's  description  of  Fusarium 
moniliforme  are  several  that  differ  from  each  other  in  more  than  one  im- 
portant character  and  are  thus  apparently  different  organisms.  For  this 
reason  and  because  none  of  the  previously  established  sections  of  the  genus 
Fusarium  fits  the  characters  of  these  corn  fungi,  a  new  section,  Moniliform, 
is  proposed." 


FIG.  22. — FUSARIUM -INFECTED  SEEDLINGS 

These  seedlings  were  apparently  fairly  vigorous,  but  the  pink  fungus 
was  clearly  evident  on  each  kernel  at  this  stage.  (See  Plate  I.)  The  data 
in  Table  ,39  show  that  seed  with  heavy  Fusarium  infection,  as  shown  in  a 
properly  conducted  germination  test,  is  inferior  for  seed  purposes. 

Miss  Grace  0.  Wineland,116  of  the  United  States  Department  of 
Agriculture  and  the  Wisconsin  Agricultural  Experiment  Station,  has 
found  the  ascigerous  stage  of  certain  strains  of  Fusarium  moniliforme 
isolated  from  corn,  all  coming  within  the  limits  of  the  section  Monili- 
form established  by  Sherbakoff. 

Corn  seedlings  infected  on  the  germinator  with  this  organism  are 
illustrated  in  Fig.  22  and  Plate  I,  Figs.  C  and  D.  The  fungus  was 
found  in  1904  on  rotting  corn  on  several  farms  in  Nebraska  and  was 
described  by  Sheldon  as  a  new  species.91  Burrill  and  Barrett10  found 
Fusarium  spp.  causing  ear  rots  in  Illinois,  but  did  not  consider  them 
as  important  a  cause  of  ear  rots  as  Diplodia  zeae.  Pammel,  King,  and 
Seal75  described  a  root  and  stalk  rot  of  corn  and  sorghum  which  they 
believed  to  be  caused  by  Fusarium  spp.  Hoffer  and  Holbert40  called 
attention  to  the  fact  that  Fusarium  spp.  are  among  the  harmful  or- 
ganisms associated  with  the  corn  root,  stalk,  and  ear  rot  diseases. 
Valleau,108  of  the  Kentucky  Agricultural  Experiment  Station,  found 


266 


BULLETIN  No.  255 


[August, 


FIG.  23. — CORN  FROM  NEARLY  DISEASE-FREE  SEED 

This  yielded  at  the  rate  of  66.3  bushels  per  acre.  U.  S.  Department 
of  Agriculture  experimental  plots  on  the  farm  of  Mr.  E.  D.  Punk, 
Bloomington.  (Compare  with  Fig.  24.) 


FlG.    24. — CORNT   FROM    FUSARIUM-INFECTED    SEED 

This  yielded  at  the  rate  of  60.9  bushels  per  acre.     U.  S.  Department 
of  Agriculture  plots  on  the  farm  of  Mr.  E.  D.  Funk,  Bloomington. 


1924]  CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES  267 

this  fungus  prevalent  on  a  large  number  of  samples  of  corn  from  Ken- 
tucky and  other  states. 

Manns  and  Adams,68- 69  of  the  Delaware  Agricultural  Experiment 
Station,  in  studying  the  distribution  and  prevalence  of  parasitic  fungi, 
found  that  this  fungus,  as  well  as  Diplodia  zeae,  Gibberella  saubinetii, 
and  an  organism  which  has  since  been  determined  as  Cephalosporium 
acremonium  Corda,  was  present  in  a  large  number  of  samples  of  seed 
corn  from  widely  different  sources.  Sherbakoff92  found  Fusarium 
moniliforme  to  be  the  common  Fusarium  of  corn.  Melchers  and  John- 
ston,70 of  the  Kansas  Agricultural  Experiment  Station,  in  discussing 
the  presence  of  certain  fungi  on  the  germinator,  report:  "Fusarium 
moniliforme  is  by  far  the  most  common  and  occurs  to  a  greater 
or  less  extent  on  over  95  percent  of  all  the  ears  so  far  tested." 
Others7-  8>  59«  98> 30  have  reported  studies  with  Fusarium  spp.  on  corn. 
It  is  evident  that  this  fungus  is  widely  distributed  and  that  it  has 
attracted  the  attention  of  a  number  of  workers. 

As  yet  field  inoculation  studies  have  failed  to  yield  definite  data 
concerning  the  pathogenicity  of  Fusarium  moniliforme  as  a  root  rot 
parasite  of  corn.  Several  strains  of  this  fungus  exist,  however,  and 
undoubtedly  they  differ  greatly  in  their  ability  to  parasitize  the  corn 
plant.  Various  strains  of  corn  differ  widely  in  their  susceptibility 
to  this  fungus  as  an  ear  rot  producing  organism.  Some  strains  have 
been  very  susceptible,  frequently  from  15  to  25  percent  of  the  grain 
being  damaged  by  Fusarium  ear  rot  alone.  Other  strains  growing  in 
adjacent  plots  have  been  practically  immune  from  Fusarium  ear  rots. 

It  must  not  be  inferred  that  seed  infection  with  Fusarium  monili- 
forme is  of  little  significance.  While  corn  from  seed  infected  pri- 
marily with  this  organism  usually  suffers  but  a  slightly  reduced  stand 
and  only  a  slight  reduction  in  vigor  (Figs.  23  and  24),  the  yield  of 
sound  corn  is  greatly  lowered  (Table  39).  Often  the  differences  in 
yield  between  corn  grown  from  such  infected  seed  and  from  good 
seed  are  apparent  only  after  the  crop  has  been  harvested  and  the 
ears  separated  into  sound  and  marketable  grades  on  a  uniform  mois- 
ture basis.  On  soils  lacking  lime  and  phosphorus,  however,  the  re- 
duction in  total  yield  frequently  has  been  pronounced.  Obviously, 
the  roots,  stalks,  and  ears  of  some  strains  of  corn  are  very  susceptible 
to  rot  by  this  fungus.  Seed  infection  with  this  organism  also  ap- 
parently indicates  that  the  resulting  plants  may  be  susceptible  to 
injury  from  unfavorable  environmental  conditions. 

Ears  conspicuously  rotted  with  Fusarium  may  be  recognized  by 
the  characteristic  pinkish  color  of  the  kernels  (Plate  I,  Figs.  C  and 
D,  and  Plate  V).  Frequently  a  number  of  individual  kernels  on  an 
ear  are  badly  rotted  by  Fusarium  spp.,  while  other  kernels  on  the 
same  ear  are  unaffected.  Also,  apparently  good  seed  ears  may  be 
heavily  infected  with  this  organism  (Fig.  25). 


268 


BULLETIN   No.   255 


[August, 


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CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES  269 

BLACK-BUNDLE  DISEASE 

The  black-bundle  disease  of  corn,  caused  by  the  fungus  Cephalo- 
sporium  acremonium  Cord.,  is  being  investigated  by  Dr.  Charles  S. 
Reddy,  of  the  United  States  Department  of  Agriculture,  and  James  R 
Holbert.  They81  make  the  following  statements  concerning  this  im- 
portant disease  and  the  causal  organism: 

"Usually  symptoms  of  the  black-bundle  disease  do  not  become  evident 
during  the  first  half  of  the  growing  season.  During  ear  development  vari- 
ous symptoms  may  develop,  such  as  abnormal  leaf  and  stalk  colors,  barren 
stalks,  nubbin  ears,  or  prolific  stalks.  Such  stalks  usually  show  blackened 
fibro-vascular  bundles. 

"In  every  field  of  dent,  flint,  and  sweet  corn  under  observation  by  the 
writers,  it  has  been  noted  that  many  plants  have  become  red  or  purple  on 
reaching  the  dough  stage.  The  red  coloration  appears  first  at  or  near  the 
mid-vein  of  the  topmost  leaf  and  progresses  downward  on  the  plant, 
affecting  several  leaves  before  progress  on  the  stalk  commences.  In  ex- 
treme cases  the  stalk  and  all  the  leaves  become  reddish  purple,  but  all 
gradations  between  the  initial  appearance  of  the  red  color  and  this  ex- 
treme condition  may  be  the  final  color  symptoms.  Plants  having  any 
gradation  of  this  reddening  or  purpling  are  designated  in  this  paper  as 
purple-leaf  plants. 

"This  type  of  reddening  does  not  conform  to  any  of  those  described 
by  Emerson,24  who  says  'It  is  of  interest  to  recall  in  this  connection  that 
plant  colors  of  maize — brown  no  less  than  the  red-purple  series — develop 
first  in  the  older  parts  where  growth  first  ceases,  such  as  the  lower  sheaths 
and  the  upper  parts  of  the  internodes  of  the  culm.'  However,  a  type  of 
reddening,  indistinguishable  from  the  one  encountered  in  commercial  fields, 
sometimes  occurs  in  selfed  lines  of  dent  corn.  Inoculation  of  open-fer- 
tilized dent  corn  with  a  particular  organism  (Cephalosporiutn  acremonium} 
increases  the  number  of  purple  or  red  plants. 

"This  disease  is  characterized  also  at  this  stage  of  development  of  the 
corn  plant  by  high  percentages  of  barren  stalks  and  stalks  producing  nubbin 
ears  only  [Fig.  26  of  this  bulletin].  Often  imperfectly  developed  ears  are 
observed  at  a  number  of  nodes  on  a  stalk  and  more  frequently  multiple-ear 
production  occurs  at  one  node,  showing  futile  attempts  at  prolificacy.  These 
manifestations — and  large  succulent  stalks  should  be  included — are  the 
readily  apparent  symptoms  associated  with  the  black-bundle  disease  of 
corn  and  can  be  noted  in  any  commercial  field.  When  plants  having  any 
of  these  symptoms  are  cut  open,  blackened  vascular  bundles  nearly  always 
can  be  found  in  the  nodes  and  internodes  near  the  base  and  sometimes  thru- 
out  the  stalk.  Occasionally  the  fundamental  tissue  outside  the  blackened 
vascular  tissues  becomes  browned  or  blackened,  but  usually  in  only  one 
internode  of  a  stalk.  .  .  . 

"Altho  purpling,  prolific  stalks,  barren  stalks,  nubbin  ears,  and  sucker- 
ing  are  closely  associated  with  this  disease,  the  blackened  fibrovascular 
bundles  are  considered  the  most  distinguishing  characteristic,  hence,  the 
name  Black-Bundle  Disease  of  Corn. 

"However,  the  number  of  plants  having  these  symptoms  (excluding 
the  black-bundle  symptom)  represents  only  a  small  part  of  the  total  num- 
ber of  plants  affected  by  the  disease.  Plants,  including  the  ears,  may 
appear  outwardly  healthy  yet  be  infected  from  the  crown  to  the  tassel 


270 


BULLETIN   No.   255 


[August, 


and  every  kernel  of  fine  looking  ears  may  bear  the  organism  internally. 
In  these  cases  the  presence  of  the  black  vascular  bundles  within  the  stalks 
is  the  most  distinguishing  symptom.  The  ears  may  be  diagnosed  by  plat- 
ing the  kernels  or  by  germination  in  conjunction  with  microscopic  ex- 
amination. 


FIG.    26.  —  CORN   AFFECTED    WITH    BLACK-BUNDLE 
DISEASE 

Barren  stalks  and  stalks  with  multiple  ears  are 
extreme  types  of  injury  from  Cephalosporium  infec- 
tion. The  black-bundle  disease  is  responsible  for 
much  loss  to  the  corn  crop.  The  plant  on  the  left  13 
apparently  healthy. 


1924]  CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES  271 

"Infected  ears  carry  the  organism  (Ccphalosporiuni  acrcinonium)  in- 
ternally in  the  seed.  It  develops  with  the  germinating  kernel  and  causes 
a  systemic  infection  of  the  plant  thru  the  vascular  system.  By  this  means, 
it  invades  the  ears  and  eventually  the  kernels.  In  this  manner  it  is  car- 
ried over  to  the  following  season.  Occasionally  an  ear  can  be  found  which 
is  externally  overrun.  In  observations  extending  over  a  period  of  three 
years,  only  one  such  ear  has  been  found.  Probably  an  especially  damp 
harvest  season  or  poor  storage  conditions  are  necessary  for  this  develop- 
ment. It  seems  possible  that  with  such  development,  the  infection  might 
spread  from  ear  to  ear.  .  .  .  The  question  of  soil  infection  has  not  been 
determined  definitely  as  yet. 

"Seed  infection  can  be  determined  macroscopically  on  limestone-saw- 
dust germinators,  .  .  .  but  the  symptoms  are  easily  overlooked  so  that 
up  to  the  present  only  a  fair  degree  of  accuracy  has  been  attained  by  this 
method. 

"Infected  germinating  kernels  have  blanched,  white  tips,  sometimes  with 
noticeable  mycelial  growth.  Often,  however,  the  mycelial  growth  cannot 
be  seen  until  examined  microscopically.  When  the  symptoms  on  the  germi- 
nator  are  overlooked,  the  ears  often  are  chosen  for  seed  because  germination 
and  the  vigor  of  the  infected  seedlings  are  seldom  impaired  at  this  time.  .  .  . 

' '  Cephalosporium  acremonium  has  been  isolated  from  black-bundles  in 
first  leaves,  from  bundles  in  stalks,  from  the  shanks,  from  the  cobs,  and 
from  the  kernels.  .  .  . 

"To  reduce  losses  from  this  disease,  it  is  well  to  avoid  selection  of  seed 
ears  from  stalks  having  any  of  this  group  of  symptoms.  Probably  the  best 
measure  of  control  will  come  with  the  development  of  resistant  strains  of 
corn  within  the  varieties." 


MISCELLANEOUS    EAR    ROTS    AND    MOLDS 

When  corn  is  injured  by  ear  worms  (Chloridea  obsoleta)  before  it 
is  well  dented,  considerable  damage  may  follow  from  ear  rots  caused 
by  fungi  other  than  Diplodia  and  Fusarium  spp.  These  include 
Aspergillus  spp.,  Penicillum  spp.,  and  other  molds.  Of  these,  the 
black  and  yellow  molds,  caused  by  Aspergillus  niger  and  Aspergillus 
flavus  Link,  respectively,  are  common.  Taubenhaus,102  of  the  Texas 
Agricultural  Experiment  Station,  reports  that  these  two  molds  are 
very  common  in  that  state  and  cause  much  damage  to  the  corn  crop. 
He  further  states : 

"There  are  cases  of  late  infection  where  the  ears  were  but  slightly  in- 
jured by  the  black  mold,  infection  being  confined  to  the  place  of  injury 
from  the  ear  worm  and  resulting  in  an  ear  more  or  less  normally  developed 
and  apparently  containing  well  nourished  and  fully  developed  grains,  altho 
their  surface  may  be  covered  with  spores  of  Aspergillus  niger." 

Taubenhaus  found  that  seed  corn  from  such  ears  was  inferior  for 
seed  purposes  and  recommended  that  only  healthy  kernels  of  abso- 
lutely healthy  ears  should  be  used  for  seed.  Altho  these  two  molds 
probably  do  not  cause  any  serious  damage  to  the  corn  crop  in  Illi- 
nois, nevertheless  they  do  occur  in  some  seasons.  The  authors  have 


272  BULLETIN  No.   255  [August, 

examined  certain  lots  of  seed  ears  which  bore  evidence  of  considerable 
damage  apparently  from  this  source. 

Both  the  black  and  the  yellow  molds  frequently  occur  in  the  test- 
ing of  corn  on  the  germinator.  Owing  to  the  fact  that  the  organism 
causing  the  black  mold  produces  an  abundance  of  black  spores  on  the 
germinator,  it  often  is  mistaken  by  inexperienced  persons  for  smut, 
which  is  an  entirely  different  fungus  and  one  which  does  not  appear 
on  the  germinator.  Ordinarily,  however,  in  a  properly  conducted 
germinator  test  of  well  selected  and  properly  stored  seed  neither  the 
black  nor  the  yellow  mold  appears. 

Where  early  selected  seed  is  not  properly  cured  and  properly 
stored,  a  large  number  of  facultative  parasites  may  grow  over  the 
butts  of  the  cobs  (Plate  IV)  and  spread  over  the  surfaces  of  the  ears. 
In  many  cases,  these  fungi  may  actually  penetrate  the  kernels  and 
seriously  affect  their  seed  value.  Under  moist  weather  conditions,  corn 
left  in  the  field  after  heavy  killing  frosts  also  may  become  infected, 
not  only  with  Diplodia  zeae  and  Fusarium  moniliforme,  but  with  a 
large  number  of  fungi  which  under  ordinary  conditions  are  sapro- 
phytes. Tine,  seed  value  of  corn  subjected  to  such  unfavorable  field 
or  storage  conditions  is  very  questionable. 

BACTERIAL  WILT 

(Stewart's  Disease) 

Bacterial  wilt,  caused  by  Aplanobacter  stewarti  (E.  F.  S.)  McCul., 
is  the  source  of  much  damage  to  sweet  corn97'  95> 80  and  also  occurs 
to  some  extent  in  dent  corn.  In  sweet  corn  the  symptoms  are  rather 
distinctive  and  easily  recognized  (Fig.  27).  The  organism  causing 
this  disease  usually  confines  its  activities  to  the  fibrovascular  bundles, 
in  which  it  multiplies  and  eventually  causes  a  clogging,  thus  stopping 
the  transpiration  stream.  By  cutting  the  stalks  of  diseased  plants 
obliquely,  the  yellow  affected  bundles  are  seen  readily.  After  the  cut 
surface  has  been  exposed  for  a  few  minutes,  yellow  bacterial  ooze 
exudes  in  small  beads  at  the  cut  end  of  the  bundles.  If  these  sticky 
beads  are  touched  with  the  finger  or  a  knife  blade,  they  may  be  drawn 
out  in  threads.  In  older  plants  the  infected  bundles  sometimes  present 
a  dark  appearance.  Leaves  of  affected  sweet  corn  plants  may  or  may 
not  turn  yellow  before  wilting,  according  to  the  extent  of  infection 
and  to  environmental  factors.  In  some  cases  plants  with  well  devel- 
oped ears  may  wilt  and  die  within  a  few  days.  The  disease  is  seed 
borne  and  apparently  does  not  live  over  winter  in  the  soil. 

On  dent  corn  the  symptoms  (Fig.  28)  are  not  so  pronounced,  and 
the  yellow  substance  in  the  infected  bundles  is  not  so  viscous.  How- 
ever, Reddy  has  shown  that  the  causal  organism  from  either  dent, 
sweet,  or  flint  corn  is  equally  parasitic  on  the  other  two  species  of  corn. 


1924] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


273 


Altho  this  disease  is  of  great  economic  importance  in  sweet  corn 
production,  there  is  no  evidence  to  date  that  it  causes  any  material 
loss  in  dent  corn. 

A  bacterial  disease  of  corn  in  Illinois  was  described  by  Burrill9 
in  1889,  but  only  a  few  scattered  reports  of  its  occurrence  in  this  state 


FIG.  27. — BACTERIAL  WILT   (STEWART'S  DISEASE)   OF  SWEET 

CORN 

The  hill  at  the  left  shows  severe  infection.  Bacterial  wilt 
is  the  source  of  much  damage  to  sweet  corn,  and  also  occurs 
to  some  extent  in  dent  corn. 

have  been  made  during  the  past  several  years.  It  seems  probable 
that  this  disease,  in  part  at  least,  is  the  root  and  stalk  rot  of  corn 
described  more  accurately  by  Rosen84  of  the  Arkansas  Agricultural 
Experiment  Station,  and  the  causal  organism  named  Pseudomonas 
dissolvens.85 

Hoffer  and  Holbert40  include  Pseudomonas  spp.  among  the  or- 
ganisms associated  with  disease  in  corn.    Reddy  has  isolated  bacteria 


274 


BULLETIN   No.   255 


from  diseased  corn  plants,  and  Reddy  and  Holbert81  make  the  follow- 
ing statement : 

"Occasionally  bacteria  arc  found  associated  with  Ccphalosporium 
acremonium  in  the  infected  bundles,  especially  in  the  lower  internodes.  In 
fact,  it  was  suspected  that  bacteria  might  play  an  important  part  in  caus- 
ing certain  of  these  disease  manifestations.  Even  yet,  the  exact  status  is 
not  fully  clear  in  this  respect,  but  is  being  investigated  further." 

GIBBERELLA  ROOT  ROT,  EAR  ROT,  AND  SEEDLING  BLIGHT  OF  CORN 

In  1919  and  1920  Dickson,  Johann,  and  Wineland17  found  that 
Gibberella  saubinetii  (Mont.)  Sace.  was  the  cause  of  practically  all  the 
wheat  scab  thruout  the  corn  belt  and  of  94  to  98  percent  of  all  the 
wheat  scab  in  the  United  States.  This  organism  also  causes  scab  of 
other  cereals.  Selby  and  Manns,89  Pammel,  King,  and  Seal,75  and 
other  workers  have  observed  Gibberella  saubinetii  on  corn  stalks.  In 
1918  Hoffer,  Johnson,  and  Atanasoff41  reported  a  greater  abundance 

of  wheat  \  scab  where  wheat 
followed  corn  that  had  been 
infected  with  the  root  and 
stalk  rots.  They  produced 
scab  by  inoculating  wheat 
with  Gibberella  spores  from 
old  diseased  corn  stalks,  and 
also  produced  root  rot  and 
seedling  blight  of  corn  under 
laboratory  conditions  by  in- 
oculating with  a  culture  of 
this  organism  from  scabbed 
wheat. 

Since  that  time  other  work- 
ers45' 2  have  reported  observa- 
tions and  presented  data 
which  show  that  the  host 
range  of  this  organism  in- 
cludes both  wheat  and  corn. 
A  rather  complete  report  on 
this  situation  is  presented  by 
Koehler,  Dickson,  and  Hol- 
bert.60 They  found  that : 

"The  yield  of  corn  suscepti- 
ble to  root  rot  was  considerably 
reduced  where  corn  followed 
badly  scabbed  wheat  in  the  rota- 


FIG.  28. — BACTERIAL  WILT  OF  DENT  CORN 
Left,  an  apparently  healthy  dent  corn 
plant;  right,  a  plant  growing  in  an  ad- 
jacent hill  badly  affected  with  bacterial 
wilt. 


tion.  Gibberella  saubinetii  was 
the  principal  organism  isolated 
from  scabbed  wheat  heads.  The 


1924} 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


275 


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CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES 


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278 


BULLETIN   No.   255 


[August, 


same  organism  was  found  very  abundantly  on  old  corn  stalks.  The  above 
organism  when  used  as  inoculum  on  disease-susceptible  corn  caused  a  con- 
siderable decrease  in  stand,  general  vigor,  and  yield." 
They  also  found  that  highly  resistant  corn  did  not  suffer  much  reduc- 
tion in  yield  when  grown  after  scabbed  wheat  or  when  inoculated  with 
a  pure  culture  of  the  organism. 

The  spores  of  G.  saubinetii  on  infected  wheat  heads  and  old  in- 
fected corn  stalks'  are  carried  by  air  currents,  and  perhaps  are  dis- 
seminated by  a  number  of  other  agencies.  Many  of  these  wind-blown 
spores  lodge  on  corn  plants,  where  they  find  a  favorable  medium  for 


Char,  of  root 
dev  of  strains 


Strong     • 


Weak 


Final  fie/d  stand  (%J 


10       20       30      40       50       60       70      80       90      100 


Uninoculate. 

zni 

Inoculated 


Reduction  following  /noculation 
with  G.  saubinetii 


Plant  Yield  (fbsj 

.200          300  .400          .500 


600 


JOO 


Strong 


Weak 


CHART  2. — EFFECT  ON  STRONG-  AND  WEAK-ROOTED  INBRED  STRAINS 

OF  INOCULATION  WITH  Gibberella  scwbinetii 

Field  stands  of  the  weak-rooted  strains  were  greatly  reduced 
following  inoculation  with  G.  saubinetii,  but  the  yield  of  surviving 
plants  was  not  reduced  as  much  in  proportion  as  the  plant  yield  of  the 
strong-rooted  strains,  the  field  stands  of  which  were  reduced  only 
slightly  by  the  inoculation  (Table  3). 


19X4]  CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES  279 

growth  in  the  moist  pollen  and  dust  collected  on  the  ligules  at  the 
bases  of  the  leaves,  between  the  sheaths  and  stalks,  and  in  the  cavities 
surrounding  the  shanks.  Late  in  the  fall  and  in  the  following  sum- 
mer perithecia  may  develop  in  abundance  near  the  nodes  of  infected 
corn  stalks.  Under  certain  conditions  G.  saubinetii  may  do  damage 
as  an  ear  rot  producing  organism. 

Manns  and  Adams69  report  a  rather  heavy  infection  of  this  or- 
ganism in  seed  corn  from  certain  states.  In  Illinois  such  infection 
has  not  been  general.  However,  various  lots  of  seed  have  been  ex- 
amined which  contained  from  10  to  15  percent  or  ears  infected  with 
G.  saubinetii.  The  use  of  seed  infected  with  this  organism  has  re- 
sulted in  greatly  reduced  stands  and  reduced  vigor,  especially  in 
early  plantings.  It  seems  evident  that  in  Illinois  G.  saubinetii  does 
considerable  damage  to  corn  in  the  role  of  a  parasitic  soil  organism 
causing  root  rot  and  seedling  blight.  There  is  no  evidence  that  this 
fungus  produces  a  systemic  infection  of  the  plant,  but  under  certain 
environmental  conditions  already  mentioned,  it  may  do  considerable 
damage  to  the  corn  crop  by  attacking  underground  parts  of  the 
plant.  Infected  plants  frequently  are  blighted  and  in  severe  cases 
die  (Fig.  29).  The  extent  of  injury  caused  by  this  soil  parasite, 
however,  cannot  be  measured  alone  by  loss  in  stand  due  to  seedling 
blight.  Certain  strains  of  corn  which  may  produce  little  evidence 
of  seedling  blight  following  inoculations  with  pure  cultures  of  this 
organism,  may  show  marked  reductions  in  vegetative  growth  during 
the  early  summer,  which  are  reflected  in  notably  reduced  yields  of 
grain  (Fig.  30).  Data  showing  such  reduction  in  field  stand  and  in 
yield  of  grain  by  G.  saubinetii  are  presented  in  Table  3  and  Chart  2. 

CORN  SMUT 

The  boil  smut,  or  common  smut,  of  corn  caused  by  Ustilago  zeae 
(Beckm.)  Ung.  is  a  familiar  disease  (Figs.  31  and  32).  At  times  it 
has  been  known  to  produce  heavy  losses  in  Illinois,  especially  in  fields 
planted  with  corn  very  susceptible  to  smut.  During  these  investiga- 
tions the  authors  have  observed  many  instances  where  plots  grown 
from  seed  infected  with  disease-producing  organisms  were  damaged 
decidedly  more  by  smut  than  adjacent  plots  grown  from  good  seed 
of  the  same  variety.  Very  frequently  strains  of  corn  susceptible  to 
root,  stalk,  and  ear  rot  diseases  have  proved  very  susceptible  to  in- 
jury from  smut.  Altho  smut  can  be  distinguished  readily  from  corn 
rot  diseases  and  altho  it  is  caused  by  a  widely  different  organism,  it 
is  possible  that  plants  weakened  by  one  of  these  diseases  may  become 
predisposed,  under  certain  conditions,  to  injury  from  the  other  dis- 
ease. 

Jones,55  of  the  Connecticut  Agricultural  Experiment  Station,  in 
1918  called  attention  to  the  fact  that  segregates  from  inbred  strains 


280 


BULLETIN  No.  255 


[August, 


of  corn  varied  widely  in  resistance  and  susceptibility  to  smut.  In 
connection  with  their  corn-breeding  work,  the  authors  of  this  bulletin 
have  observed  numerous  instances  in  which  certain  inbred  strains 
were  almost  completely  ruined  by  smut,  while  other  strains  in  adja- 
cent rows  were  affected  only  slightly.  More  recently,  work  by  Dr. 
W.  H.  Tisdale  with  strains  of  corn  supplied  by  Mr.  C.  H.  Kyle,  of 
the  United  States  Department  of  Agriculture,  has  established,  beyond 
doubt,  the  fact  of  inherited  resistance  and  susceptibility  to  this  dis- 
ease. Open-pollinated  strains  of  corn  which  have  been  selected  by  the 
authors  over  a  period  of  years  from  plants  not  affected  with  smut,  have 
been  injured  but  slightly  by  this  disease.  Thus  the  recommendation 
to  avoid  ears  from  smutted  plants  in  the  selection  of  seed  corn  is  well 
founded,  and  furnishes  an  effective  means  for  the  control  of  this 
disease. 

Common  corn  smut  attacks  only  above-ground  parts  of  the  corn 
plant.  The  organism  overwinters  in  soil,  manure,,  and  compost.  It 
spreads  by  means  of  small  spores  (sporidia),  which  are  carried  by 
air  currents.  These  spores  lodge  on  the  corn  plant  and  usually  infect 
thru  stomata  and  wounds.  Mechanical  injuries  to  the  plant,  therefore, 
make  possible  a  severe  attack  of  smut,  especially  on  susceptible  strains 
of  corn. 


FIG.  31. — CORN  SMUT 

Altho  smut  can  be  distinguished  readily  from  the  corn  rot  diseases 
and  altho  it  is  caused  by  a  widely  different  organism,  it  is  possible  that 
plants  weakened  by  one  of  these  diseases  may  become  predisposed,  under 
certain  conditions,  to  injury  from  the  other  disease. 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


281 


FIG.  32. — CORN  SMUT 

An  effective  means  to  control  this  disease  is  to  avoid  the  use  of  seed  from 
smutted  plants. 

Head  smut  of  corn,79  caused  by  Sphacclotheca  reiliana  (Kiihn) 
Clinton,  occurs  only  in  the  semi-arid  Middle  West  and  to  a  certain 
extent  on  the  Pacific  coast.10  According  to  Dr.  W.  H.  Tisdale,  it  is 
not  a  serious  problem  in  any  locality  in  the  United  States. 


MISCELLANEOUS   SOIL-BORNE   DISEASES 

In  addition  to  the  disease-producing  organisms  already  mentioned 
that  may  be  soil-borne,  there  are  certain  other  organisms  in  the  soil 
which  may  parasitize  the  co'rn  plant  under  certain  environmental  con- 
ditions. Stover,"  working  at  the  University  of  Wisconsin  in  1921, 
reports  the  following: 

"A  species  of  Helmintliosporium  isolated  from  living  corn  plants  was 
found  to  cause  a  marked  seedling  blight  of  corn,  .  .  .  mesocotyl,  coty- 
ledonary  node,  and  seminal  roots  were  rotted.  The  diseased  region  was 
dark  brown  to  deep  black  and  usually  shrunken." 

This  same  investigator  found  that  the  disease  was  more  severe  with 
soil  temperatures  between  16°  and  24°  C.  He  also  says: 

"A  relatively  high  moisture  content  of  the  soil  is  favorable  for  the 
development  of  the  disease." 


282  BULLETIN  No.  255  [August, 

CORN  RUST  AND  OTHER  DISEASES 

Traces  of  corn  rust  caused  by  Puccinia  sorghi  Sehw.  can  be  found 
in  almost  every  cornfield,  but  only  a  few  fields  have  been  observed 
where  this  disease  has  resulted  in  any  appreciable  damage  to  the  crop. 
Different  strains,  as  well  as  individual  plants,  vary  widely  in  re- 
sistance and  susceptibility  to  rust,  as  noted  by  Weber,113  and  by 
Mains,  Trost,  and  Smith,67  and  as  observed  by  the  authors.  Certain 
inbred  strains  have  been  grown  which  were  very  susceptible,  both 
leaves  and  sheaths  becoming  covered  with  rust  pustules,  while  other 
inbred  strains  of  the  same  variety  in  adjacent  plots  were  practically 
free  from  rust.  By  avoiding  seed  ears  from  rusted  plants,  it  seems 
unlikely  that  this  disease  will  ever  become  economically  important 
under  conditions  existing  in  Illinois. 

Brown  spot  of  corn,  caused  by  Physoderma  zeae-maydis  Shaw, 
causes  considerable  damage  in  dent  corn  in  the  South  Atlantic  and 
Gulf  states.  It  was  observed  in  Illinois  by  Burrill  in  1911.  Since 
then  occasional  plants  affected  with  this  disease  have  been  found  al- 
most every  year,  but  no  instance  of  severe  damage  has  been  reported 
in  Illinois  except  on  sweet  corn.  A  complete  discussion  of  this  dis- 
ease is  given  by  Tisdale.105 

Durrell,21  of  the  Iowa  Agricultural  Experiment  Station,  has  de- 
scribed a  purple-leaf  sheath  disease  of  corn  caused  by  the  growth  of 
facultative  parasites  on  pollen  accumulated  between  the  leaf  sheaths 
and  the  stalks.  Other  leaf -sheath  rottings  not  described  by  this  in- 
vestigator appear  before  any  pollen  has  been  shed.  These  troubles 
may  cause  slight  injuries  under  certain  conditions. 

Mosaic  disease  of  corn6  has  been  reported  in  the  United  States  but 
losses  in  the  corn  crop  due  to  this  disease  probably  are  very  slight. 
At  the  present  time  this  disease  is  confined  mostly  to  the  regions 
producing  sugar  cane. 

Downy  mildew  of  maize,  caused  by  Sclerospora  spp.,  results  in 
serious  losses  in  the  Orient.  Up  to  the  present  time  it  has  not  been 
known  to  occur  in  the  United  States.  An  investigation  of  this  disease 
in  the  Philippines  has  been  reported  by  West  on.114 


1984]  CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES  283 


The  importance  of  environmental  factors  in  determining  growth 
and  development  of  plant  life  was  recognized  by  the  earliest  agri- 
cultural workers.  The  relation  of  environing  factors  to  the  develop- 
ment of  plant  disease  also  has  been  observed  in  a  general  way  by 
farmers  and  plant  culturists  for  many  years.  More  recently  certain 
of  these  soil  and  climatic  factors  have  been  the  subject  of  much  in- 
vestigation in  connection  with  the  occurrence  of  diseases  in  field  crops. 
The  relation  of  environment  to  the  development  of  the  corn  rot  dis- 
eases under  discussion  in  this  bulletin  is  a  very  complex  problem,  even 
a  partially  complete  understanding  of  which  will  require  years  of 
careful  study.  However,  certain  data  have  accumulated  during  the 
progress  of  the  investigations  which  throw  considerable  light  on  these 
complicated  relationships. 

Altho  it  is  possible,  under  properly  controlled  greenhouse  condi- 
tions, to  determine  the  influence  of  soil  moisture,  soil  aeration,  and 
certain  other  factors  on  the  development  of  the  corn  rot  diseases,  yet 
it  must  be  recognized  that  such  environing  factors  seldom,  if  ever, 
act  independently  under  actual  field  conditions.  A  change  in  one 
factor  usually  is  accompanied  by  changes  in  other  factors,  as  well  as 
by  changes  in  the  biological  and  chemical  conditions  of  the  soil,  some 
of  which  may  profoundly  affect  the  normal  metabolism  of  the  corn 
plant  and  its  resistance  and  susceptibility  to  the  corn  rot  diseases. 
But  in  spite  of  the  complexity  of  the  situation,  much  progress  al- 
ready has  been  made  in  obtaining  a  clearer  understanding  of  the  rela- 
tion of  certain  environing  factors  to  the  development  of  such  diseases 
as  cabbage  yellows,56-  29  flax  wilt,104  root  rot  of  tobacco,53  Rhizoctonia 
of  potatoes,82  potato  scab,57  seedling  blight  of  wheat,19  and  other 
diseases. 

SOIL  TEMPERATURE  AND  TIME  OF  PLANTING 

The  effects  of  soil  and  air  temperature  on  the  corn  plant  itself 
are  very  marked  and  have  been  studied  by  a  number  of  investiga- 
tors.87-33' 4»  nit  35  When  the  temperature  is  too  low  following  plant- 
ing, the  leaves  turn  yellow  and  the  plants  grow  very  slowly.  On  the 
other  hand,  a  very  high  temperature  with  an  abundance  of  moisture 
following  planting  produces  a  tall,  spindly  growth.  Dickson19  and 
others  have  shown  that  the  ratio  of  tops  to  roots  of  corn  is  influenced 
by  soil  temperatures  during  this  stage.  A  rather  cool  temperature 
favors  root  development,  while  a  high  temperature  favors  shoot  de- 
velopment. The  sturdy  growth  of  the  young  plant  essential  for  the 
best  results  is  obtained  only  within  a  comparatively  limited  range  of 
temperature,  which  usually  obtains  in  this  latitude  during  the  second 
or  third  week  in  May.  Each  stage  of  development  in  the  corn  plant 
is  best  produced  within  certain  ranges  of  temperature,  a  departure 


284 


BULLETIN  No.   255 


[August, 


from  which  disturbs  the  normal  activities  of  the  plant  and  may  favor 
the  attack  of  certain  disease-producing  organisms  if  the  particular 
strain  of  corn  is  disease-susceptible. 

Dickson,18  as  stated  above,  found  that  the  temperature  of  the  soil 
was  ' '  the  most  important  single  factor  determining  the  extent  of  seed- 
ling blight"  caused  by  Gibberella  saubinetii.  Both  field  plantings 
and  controlled  greenhouse  experiments  by  Dickson  showed  that  Gib- 
berella blighting  of  corn  developed  most  abundantly  in  soil  tempera- 
tures under  66°  F. 

Field  data  are  presented  in  Table  4  and  Chart  3  showing  the  effect 
on  yield  of  early  and  late  planting  following  inoculation  with  Gib- 
berella saubinetii.  These  experiments  were  located  on  soil  that  was 
almost  ideal  from  the  standpoint  of  drainage,  balanced  fertility,  and 


Date  of 
planting 

May  II 
May  28 


Field  stand  (%J 


o 


10         2O       30        4O        50        60         7O        80        90        100 


Uninoculated 

^-^ 

noculaten/ 


Percentage  strong  plants 
Acre  yield  (bu.) 

3O        4O          50         60          70         80        90         IOO 


Uninoculoitea 

~r-r 

Inoculated 


May  II 


May  28 


H^l  Sound  corn 

CHAKT   3. — INFLUENCE  OP  EARLY  AND   LATE  PLANTING  ON  INJURY 
FOLLOWING  INOCULATION  WITH  Gibberella  saubinetii  (Table  4) 
There  were  marked  reductions  in  percentage  field  stand,  percent- 
age of  strong  plants,  and  acre  yield  following  inoculation  with   G. 
saubinetii  in  the  early  planting,  but  only  slight  reductions  in  the  late 
planting. 


1924} 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


285 


physical  condition.  In  the  planting  made  on  May  11,  when  the  mean 
soil  temperature  was  approximately  58°  F.,  the  stand  was  greatly  re- 
duced by  the  inoculation,  whereas  in  the  late  planting  made  on  May 
28,  when  the  mean  soil  temperature  was  above  68°  F.,  it  was  reduced 
only  slightly.  Again,  in  the  early  planting  the  percentage  of  vigorous 
plants  was  reduced  from  78.8  percent  in  the  uninoculated  plots  to 
57.8  percent  in  the  inoculated.  Both  total  yield  and  yield  of  sound 
corn  also  were  affected  by  the  inoculation,  the  reduction  of  13.0  bush- 
els per  acre  in  total  yield  and  10.2  bushels  in  sound  corn  being  very 
significant  in  terms  of  the  odds  involved.  In  the  late  planting  there 
was  little  reduction  in  vigor  and  no  significant  reduction  in  either 
total  yield  or  yield  of  sound  corn.  These  data,  as  well  as  those  pre- 
sented by  Dickson,  indicate  that  soil  temperature  is  a  very  important 

TABLE  5. — INFLUENCE  OP  DATE  OF  PLANTING  ON  YIELD  FROM  GOOD  SEED 
AND  FROM  SCUTELLUM-ROTTED  SEED 

Grown  on  brown  silt  loam  of  high  fertility,  University  South  Farm, 
Urbana,  1920-1922 


Year 

Date 
of 
planting 

Character 
of 
seed 

Acre  yield 

Reduction  in 
sound  corn  fol- 
lowing use  of 
susceptible  seed 

Total 

Sound 

1920 

May  19  
May  26  
June  2 

Good 

bu. 
79.7 
73.4 

79.3 
65.8 

77.8 
61.9 

bu. 
70.4 
58.9 

66.9 
48.3 

56.8 
39.7 

bu. 
11.5 

18.6 
17.1 

perct. 
16.3 

27.8 
30.1 

Susceptible  

Good  

Susceptible  

Good  

Susceptible  

1921 

May    2  
May  10  
May  20  
May  31  .... 

Good  

100.7 
90.9 

99.8 
•86.3 

90.5 
77.0 

89.9 
79.0 

89.6 
73.4 

85.2 
69.4 

79.1 
57.4 

76.6 
55.9 

16.2 
15.8 
21.7 
20.7 

18.1 
18.5 
27.4 
27.0 

Susceptible  

Good  

Susceptible  

Good  

Susceptible  

Good  

Susceptible  

1922 

May    4  
May  13  
May  22  
May  31  

Good  

59.2 
57.5 

58.3 
54.6 

56.1 

44.7 

53.0 
41.0 

45.0 
43.9 

44.8 
42.1 

46.6 
33.4 

45.5 
33.2 

1.1 
2.7 
13.2 
12.3 

2.4 
6.0 
28.3 
27.0 

Susceptible  

Good  

Susceptible  

Good  

Susceptible  

Good  

Susceptible  

286 


BULLETIN  No.  255 


[August, 


factor  in  determining  the  extent  of  damage  caused  by  G.  saubinetii 
when  seed  of  strains  susceptible  to  this  organism  is  used. 

Altho  soil  temperature  is  only  one  of  many  factors  involved  in 
different  dates  of  planting,  yet  it  is  a  very  important  one.  On  that 
account  data  on  the  influence  of  date  of  planting  on  the  development 
of  the  scutellum  rot  and  Diplodia  diseases  are  presented  in  the  dis- 
cussion of  this  factor.  Data  relating  to  the  scutellum  rot  disease  are 
given  in  Table  5  and  Chart  4;  the  appearance  of  the  corn  grown 
from  such  seed  is  illustrated  in  Fig.  33.  In  each  of  the  three  years 
reported  the  time-of-planting  factor  proved  to  be  very  influential  in 
determining  the  comparative  yields  of  corn  grown  from  scutellum- 
rotted  seed.  Corn  grown  from  good  seed  was  affected  much  less  by 
late  planting  than'  corn  from  scutellum-rotted  seed.  These  data  indi- 
cate that  corn  grown  from  scutellum-rotted  seed  is  affected  adversely 
by  conditions  usually  accompanying  late  planting  (Fig.  34).  One  of 
the  most  important  of  these  environing  factors  is  high  soil  temperature. 

Certain  data  on  the  relation  of  time  of  planting  to  the  behavior 
of  corn  grown  from  good  seed  and  from  Diplodia-infected  seed  are 
given  in  Table  6  and  Chart  5.  The  planting  made  on  May  7  was  one 


y/e/d  of  -Sound  Com  G/vwt  from  Scute/tum-Rottect 

Seed/n  Bushels  per  Acre 
70     6O     50    <fo    30     20 


80 


10 


Increase  in  Production 
Due  to  Use  of  Good  deed 

/O      20     3O 


19204 


/92I  4 


/922\ 


Mau  19 


Mau  26 


June  2 


Mau  2 


Mau  10 


Mau  20 


Mau3/ 


Mau 


Mau  13 


Mau  22 


~L 


OS 


CHART  4. — YIELD  FROM  SCUTELLUM-ROTTED  SEED  AS  AFFECTED  BY  DATE  OF 

PLANTING 

Reductions  in  yield  of  corn  from  scutellum-rotted  seed  as  compared 
with  corn  grown  from  good  seed  usually  are  greater  in  the  later  plantings 
than  in  the  earlier  plantings  (Table  5). 


1984] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


287 


TABLE  6. — INFLUENCE  OF  DATE  OF  PLANTING  ON  YIELD  FROM  GOOD  SEED 
AND  FROM  DlPLODIA-lNFECTED  SEED 

Yellow  dent  corn  grown  on  brown  silt  loam  of  medium  high  fertility, 
near  Bloomington,  1921 


Date  of 
planting 

Character  of  seed 

Number  of 
replications 

Mean 

acre  yield 

Reduction    following 
use  of  infected  seed 

May    7  ... 
May  14  ... 
May  21  ... 
May  30  ... 

Good  seed             .  .  . 

5 
5 

5 
5 

5 
5 

5 
5 

bu. 
66.0  +  1.3 
40.5  ±  1.2 

66.3  +  1.2 
52.9  ±  3.0 

68.0  +  0.7 
53.7  +  1.7 

71.0  +  2.5 
38.1  ±  0.8 

bu. 
25.5  ±  1.8 

13.4  ±  3.2 
14.3  +  1.8 
32.9  ±  2.6 

perct. 
38.6 

20.2 
21.0 
46.3 

Diplodia-infected  .  .  . 
Good  seed 

Diplodia-infected  .  .  . 
Good  seed  

Diplodia-infected  .  .  . 
Good  seed  

Diplodia-infected  .  .  . 

of  the  first  in  the  locality  in  which  the  experiment  was  conducted.  The 
soil  was  still  comparatively  cold  and  rather  moist.  As  the  season 
advanced  the  soil  became  warmer  rather  gradually.  At  the  time  of 
the  last,  or  fourth,  planting  and  for  several  days  thereafter,  the  soil 


May  7         May  14         May  21         May  30 

Reduction  in  yield  from  Diplodia-infected  seed 


CHART  5. — YIELD   FROM   DIPLODIA-INFECTED  SEED  AS  AFFECTED  BY 
DATE  OF  PLANTING 

Reductions  in  yield  of  corn  from  Diplodia-infected  seed,  as  com- 
pared with  corn  from  good  seed,  are  usually  greatest  in  the  early 
planting  and  gradually  decrease  in  subsequent  plantings.  The  ex- 
ception to  this  general  statement  occurs  when  a  planting  is  accom- 
panied by  high  moisture,  in  which  event  the  yields  may  be  reduced 
even  more  than  in  the  earliest  planting  (Table  6). 


288 


BULLETIN   No.   255 


[August, 


FIG.    33. — REDUCTION    IN    HEIGHT    OF    LATE    PLANTINGS    OF    SCUTELLUM- 
INFECTED  CORN  (See  also  following  page) 


1924} 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


289 


(Fig.  33  cont.)  Plots  planted  at  various  dates  with  good  seed  (A)  and 
with  scutellum-rotted  seed  (B).  Note  marked  reduction  in  height  of  corn 
from  scutellum-rotted  seed  in  the  last  two  plantings.  University  South 
Farm,  Urbana. 


290 


BULLETIN   No.   255 


[August, 


temperature  was  comparatively  high.    A  few  days  prior  to  the  plant- 
ing on  May  30  there  were  heavy  rains. 

The  data  show  that  time  of  planting  with  its  accompanying  com- 
plex of  soil  factors  has  a  very  pronounced  influence  on  the  develop- 


Planted  withSCUH  .LUM-ROTSeed  Lot  T 


h  DISEASE  FRE 


Planted  with  DISEASE  fREE  Seed 


PlantedwftliSCin  lUMOTSeedUtl 


FIG.  34. — EFFECT  OF  LATE  PLANTING  ON  INJURY  FROM  SCUTELLUM  EOT 
U.  S,  Department  of  Agriculture  experimental  plots  near  Bloomington. 
Corn  grown  from  scutellum-rotted  seed  is  affected  much  more  adversely 
by  conditions  usually  accompanying  late  planting  than  is  corn  from  good 
seed. 


1924}  CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES  291 

ment  of  disease  in  corn  grown  from  Diplodia-infected  seed.  Of  the 
four  plantings  at  seven-day  intervals  of  corn  grown  from  Diplodia- 
infected  seed,  those  made  on  the  two  intermediate  dates  gave  higher 
yields  than  those  made  on  either  the  early  or  the  late  date.  The  dif- 
ference in  acre  yield  between  the  first  and  second  plantings  was  12.4 
bushels  and  between  the  third  and  fourth  plantings,  15.6.  The  de- 
cided reduction  probably  was  due  to  the  combination  of  high  soil 
temperature  and  high  soil  moisture.  The  yield  of  corn  grown  from 
good  seed  was  only  slightly  affected  by  the  same  changes  in  environ- 
ment. 

The  data  presented  in  Tables  7,  12,  and  13,  also  show  that  corn 
grown  from  Diplodia-infected  seed  is  affected  very  adversely  by  early 
planting  in  rather  cold  soil  (Figs.  35  and  36).  The  data  in  Table  7 
are  presented  graphically  in  Chart  6. 

Additional  data  on  the  influence  of  date  of  planting  on  the  final 
field  stand  of  corn  grown  from  good  seed  and  from  certain  lots  of 
diseased  seed  are  given  in  Table  8.  Soil  moisture  and  soil  temperature 
records  for  the  early  part  of  the  season  are  shown  in  Tables  9  and  10 
and  in  Charts  7  and  8.  With  the  exception  of  the  readings  on  May 
26,  there  was  little  variation  in  soil  moisture.  Soil  temperatures  dur- 
ing the  first  three  weeks  in  May  were  rather  unfavorable  for  corn 
germination.  Climatic  conditions  during  this  period  also  were  con- 
sidered unusually  adverse  for  corn  germination.  The  mean  soil  tem- 
peratures for  fourteen  days  following  each  planting  are  given  in 
Table  11  and  Chart  9. 

In  spite  of  the  unfavorable  conditions  all  plantings  of  the  corn 
from  good  seed  produced  a  satisfactory  field  stand,  there  being  a 
range  of  only  5.7  percent  between  the  lowest  and  highest,  which  were 

88.7  and  94.4  percent,  respectively. 

The  behavior  of  corn  grown  from  scutellum-rotted  and  from 
Diplodia-infected  seed  is  especially  interesting  in  view  of  the  un- 
usually^ adverse  conditions  prevailing  during  the  month  of  May.  In 
the  fields  planted  to  scutellum-rotted  seed,  the  increases  in  stand  from 

49.8  percent  in  the  first  planting  to  73.6  percent  in  the  second  plant- 
ing, and  to  85.1  percent  in  the  third  planting  (Table  8)  are  signifi- 
cant.   The  drop  in  field  stand  to  71.6  percent  in  the  last  planting  is 
consistent  with  the  decided  reduction  in  yield  from  scutellum-rotted 
seed  in  the  late  planting  reported  in  Table  5.    In  the  plots  planted 
to  Diplodia-infected  seed,  there  was  a  gradual  increase  in  percentages 
of  field  stands  of  corn  grown  from  the  successive  plantings,  beginning 
with  23.6  percent  in  the  first  planting  and  ending  with  66.5  percent 
in  the  last. 

Corn  from  Fusarium-infected  seed  was  consistently  lower  in  field 
stand  than  corn  from  good  seed,  but  at  no  time  was  there  a  marked 
difference  between  the  stands  of  the  various  plantings.  The  field  stand 


292 


BULLETIN   No.   255 


[August, 


TABLE  7. — INFLUENCE  OF  DATE  OF  PLANTING  ON  YIELD  FROM  GOOD  SEED 
AND  FROM  DlPLODIA-lNFECTED  SEED 

Yellow  dent  corn  grown  on  brown  silt  loam  of  high  fertility, 
near  Bloomington,  1923 


Date  of 
planting 

Character  of  seed 

Number  of 
replications 

Mean  acre 
yield  of 
sound  corn 

Reduction    following 
use  of  infested  seed 

May    7  ... 
May  24  ... 
May  31  ... 

Good      

4 
4 

7 
7 

6 
6 

bu. 
79.4  +  1.8 
42.3  ±  1.0 

83.8  +  1.1 
57.3  ±  3.4 

85.4  +  1.0 

68.2  ±  2.2 

bu. 
37.1  ±  2.1 

26.5  ±  3.6 
17.2  +  2.4 

perct. 
46.7 

31.6 
20.1 

Diplodia-infected  .  .  . 
Good            ...      . 

Diplodia-infected  .  .  . 
Good  

Diplodia-infected  .  .  . 

of  corn  grown  from  Cephalosporium-inf ected  seed,  was  decidedly  better 
in  the  third  planting  than  in  any  one  of  the  other  plantings. 

Acre  yields  of  corn  grown  from  good  seed,  scutellum-rotted  seed, 
and  Diplodia-infected  seed  planted  on  four  different  dates  on  the 
North-Central  rotation  are  given  in  Table  12  and  Chart  10.  The  early 


May  7 


May  24 


Maydf 


11111  Reduction  in  yield  from  Diplodia-infected  seed 

CHART  6. — YIELD  FROM  DIPLODIA-INFECTED  SEED  AS  AFFECTED  BY 

DATE  OF  PLANTING  (Table  7) 

Reduction  in  yield  from  Diplodia-infected  seed  was  greatest 
in  the  early  planting  and  least  in  the  late  planting. 


1984] 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


293 


EARLY  PLANTING 


INTERMEDIATE  PLANTING        . 

PlantedwilkDISEASEFBEE  Seed  m*  Planted  wi  DIPLODIA  Infected  Seed 


LATE  PLANTING 


Planted  wiihDISEASE  FREE  Seed  i«  Planted  with  DIPLODIA  Infected  Seed 


FIG.  35. — DIPLODIA  INJURY  AS  AFFECTED  BY  TIME  OF  PLANTING,  EXPERI- 
MENTAL PLOTS,  BLOOMINGTON 

Seed  of  strong  vitality  and  free  from  infection  can  be  planted  much 
earlier  than  Diplodia-infected  seed  or  seed  affected  with  scutellum  rot. 


294 


BULLETIN   No.   255 


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CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES 


295 


TABLE  9. — SOIL  TEMPERATURES  PROM  MAY  4  TO  JUNE  14,  1923, 
UNIVERSITY  SOUTH  FARM,  URBANA    (TABLE  8) 


Date 

Soil  temperatures: 

Mean  daily 
soil  temperature1 

7:00  a.  m. 

5:20  p. 

m. 

Depth 
2  in.          4  in. 

Depth 
2  in.            4  in. 

Depth 
2  in.           4  in. 

May    4  

°F. 
51.0 
51.0 
50.5 
53.0 
51.5 

39.0 
42.5 
60.0 
52.0 
45.5 

49.0 
59.0 
50.0 
50.5 
53.5 

59.0 
61.0 
51.0 
52.5 
51.0 

53.5 
56.0 
63.0 
63.5 
60.0 

64.0 
60.0 
58.0 
67.0 
68.0 

67.0 
70.0 
72.0 
70.0 
67.5 

61.0 
58.0 
61.0 
60.5 
60.0 

62.0 
65.0 

°F. 

53.5 
53.5 
53.0 
54.5 
54.0 

43.0 
44.0 
58.0 
54.0 
46.0 

49.0 
57.0 
51.0 
50.0 
53.0 

57.0 
61.0 
53.0 
53.5 
51.5 

54.5 
57.0 
63.0 
63.0 
60.0 

64.0 
62.0 
58.0 
65.0 
67.0 

67.0 
69.5 
71.0 
69.0 
67.0 

62.0 
59.0 
63.0 
62.5 
61.0 

64.0 
65.0 

°F. 

65.0 
68.0 
71.5 
65.5 
46.5 

56.5 
61.0 
52.0 
56.0 
64.0 

56.0 
61.0 
56.0 
62.0 
63.5 

69.0 
62.0 
67.0 
61.5 
67.0 

70.0 
72.0 
68.0 
70.0 
72  .  0    • 

68.0 
73.0 
80.0 
79.0 
82.0 

84.0 
85.0 
76.0 
76.5 
78.0 

77.0 
68.0 
69.0 
62.0 
74.0 

76.0 
83.0 

°F. 
63.0 
64.0 
66.0 
65.0 
50.0 

53.0 
56.5 
54.0 
55.0 
61.0 

56.0 
59.0 
56.0 
60.0 
61.0 

67.0 
62.0 
65.0 
61.0 
65.0 

68.5 
70.0 
66.0 
70.0 
70.5 

68.0 
72.5 
76.0 
77.0 
80.0 

82.5 
84.0 
79.0 
75.0 
76.0 

76.0 
67.0 
68.0 
63.0 
71.0 

73.5 
79.0 

op                     op 

58!o        58.3 
59.5         58.8 
61.0         59.5 
59.3         59.8 
49.0        52.0 

47.8        48.0 
51.8         50.3 
56.0         56.0 
54.0        54.5 
54.8        53.5 

52.5        52.5 
60.0         58.0 
53.0         53.5 
56.3         55.0 
58.5         57.0 

64.0         62.0 
61.5         61.5 
59.0         59.0 
57.0         57.3 
59.0        58.3 

61.8        61.5 
64.0        63.5 
65.5         64.5 
66.8        66.5 
66.0        65.3 

66.0        66.0 
66.5         67.3 
69.0        67.0 
73.0        71.0 
75.0        73.5 

75.5        74.8 
77.5        76.8 
74.0        75.0 
73.3        72.0 
72.8        71.5 

69.0        69.0 
63.0        63.0 
65.0         65.5 
61.3        62.8 
67.0        66.0 

69.0        68.8 
74.0         72.0 

5    

6      

7       

8       

9      

10       

11        

12            

13  

14          

15  

16  

17    

18      

19  .. 

20  

21        

22        

23              

24        

25        

26  

27  

28  

29  .. 

30  

31  

June    1  

2        

3  .. 

4  

5  

6  

7  

8... 

9  

10  

11  

12  

13.. 

14  

mean  is  the  average  of  the  temperatures  for  the  particular  depths  at  7:00 
a.  m.  and  5:20  p.  m.  for  each  day. 


296 


BULLETIN   No.   255 


[August, 


80 


75 

70 

65 
60 
55 
50 
45 
40 
35 


Mean  daily  temperature  at  2  in.  depth 
"    4  in. 


4     56     7     8    9    10  II    II  13  I*  IS  16  17  IB   19  20  Zl  22  13  !4  IS  It  27  !8  33  3031    123     456     7    8    9    IO    II   I!  13    /•» 

May  June 

CHART  7. — SOIL  TEMPERATURES  FROM  MAY  14  TO  JUNE  14,  1923,  UNIVERSITY 
SOUTH  FARM   (Table  9) 


FIG.  36. — CORN  FROM  DIPLODIA-INFECTED  SEED   (LEFT)   AND  FROM  CORN  FROM 

GOOD  SEED  (EIGHT) 

An  early  planted  experimental  series  on  University  Roland  field,  Urbana. 
Corn  grown  from  Diplodia-infected  seed  is  affected  very  adversely  by  early 
planting  in  rather  cold  soil. 


1924] 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


297 


TABLE  10. — SOIL  MOISTURE  PROM  MAY  2  TO  JUNE  13,  1923, 
UNIVERSITY  SOUTH  FARM,  URBANA    (TABLE  8) 

Mean  percentages  based  on  dry  weight 


Date  of  planting 

Number  of 
samples 

Mean  percentage 
of  soil  moisture 

May    2  

14 

perct. 
28.72  +  0.36 

3       

13 

28.44  +  0  22 

4         

14 

27.43  +  0  27 

5         

14 

26.91  +  0  30 

8         

14 

28  20  +  0  29 

11         

14 

29  06  +  0  28 

14  

14 

28.12  +  0.22 

17  

13 

31.10  +  0.31 

20  

14 

28.40  +  0.54 

23  

14 

27.73  +  0.38 

26  . 

14 

34.20  +  0.42 

29  

14 

29.07  +  0  26 

June    1         

14 

28.18  +  0  41 

4         

14 

27.64  +  0  36 

7  

14 

26.03  +  0.28 

10            

14 

27  30  +  0  44 

13  

14 

26.92  ±  0.32 

35 


2       3 

May 


//       14      17      20     23     26      29       I 


Date  of  planfinj 


June 


10      '3 


CHART  8. — PERCENTAGE  OF  SOIL  MOISTURE  FROM  MAY  2  TO  JUNE 
12,  1923,  UNIVERSITY  SOUTH  FARM   (Table  10) 

and  the  late  plantings  of  scutellum-rotted  seed  yielded  at  a  much 
lower  rate  than  the  two  plantings  at  intermediate  dates.  Corn  from 
Diplodia-infected  seed  yielded  the  least  in  the  early  plantings  and  the 
most  in  the  late  plantings. 


298 


BULLETIN   No.   255 


[August, 


Reductions  in  yield  of  corn  from  Diplodia-infected  seed,  as  com- 
pared with  corn  from  good  seed,  are  usually  greatest  in  the  early 
planting  and  gradually  decrease  in  subsequent  plantings.  The  ex- 
ception to  this  general  statement  occurs  whenever  a  planting  is  ac- 
companied by  high  moisture,  in  which  event  the  yields  may  be  re- 
duced even  more  than  in  the  earliest  planting. 

TABLE  11. — MEAN  SOIL  TEMPERATURES   FOR  FOURTEEN  DAYS  FOLLOWING  EACH 
PLANTING  (TABLE  8),  UNIVERSITY  SOUTH  FARM,  URBANA 

Taken  at  a  depth  of  2  inches 


Date  of  planting 

Mean 
minimum 
soil 
temperature 

Mean 
maximum 
soil 
temperature 

Mean 
soil 
temperature 

May    2  

op 
50  3 

°F 
60.2 

°F 
55.3 

May  14  

55  2 

64  6 

59.9 

May  21  

59  9 

72  3 

66.1 

May  31  

64.4 

76.2 

70.3 

Similar  data  from  experimental  plots  at  Ontario  Parish,  near 
Oneida,  Illinois,  are  reported  in  Table  13  and  Chart  11 ;  soil  tempera- 
ture records  kept  during  the  experiment  are  given  in  Table  14  and 
Chart  12.  These  data,  together  with  many  other  data  not  herein  re- 
ported, indicate  that  on  most  soils  of  the  corn  belt  very  early  plantings 
of  inferior  seed,  including  infected  seed,  are  likely  to  result  in  unsatis- 
factory field  stands  (Figs.  35  and  36).  They  also  indicate  that  late 
plantings  of  scutellum-rotted  seed  yield 
much  less  than  intermediate  plantings. 
Good  seed  of  strong  vitality  and  free  from 
infection  will  grow  under  a  wider  range  of 
temperature  and  moisture  and  can  be  plant- 
ed with  safety  much  earlier  than  infected 
seed  or  seed  affected  with  scutellum  rot. 

A  combination  of  high  temperature  and 
high  humidity  during  the  maturation  of 
the  corn  crop  favors  the  development  of 
certain  ear  rots,  particularly  Diplodia,  in 
disease-susceptible  strains  of  corn.  There 
are  strains  of  corn,  however,  which  are 
affected  much  less  than  others  by  ear  rots 
under  the  same  unfavorable  conditions. 
Where  all  conditions  are  ideal  for  corn,  no 
ear  rots  may  develop  on  the  ear-rot  suscepti- 
ble strains,  but  such  conditions  seldom 
prevail. 


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Ma!J     Date  of  planting 

CHART  9. — MEAN  SOIL  TEM- 
PERATURES FOR  FOURTEEN 
DAYS  FOLLOWING  EACH 
PLANTING,  UNIVERSITY 
SOUTH  FARM,  URBANA, 
1923  (Table  11) 


1924} 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


29<J 


Date  of 


Acre  Yield  (bu.) 

First  year  corn  after  clover 
20          30         40          50          60 


Second  year  corn  after  clover 


May  31  •<  \Scui-e /lum-r  1 


CHART   10. — YIELDS   FROM    SCUTELLUM-ROTTED   SEED   AND   FROM   DIPLODIA- 
INFECTED  SEED  PLANTED  AT  FOUR  DIFFERENT  DATES,  (Table  12) 

The  early  and  lato  plantings  from  scutellum-rotted  seed  yielded  at  a 
much  lower  rate  than  the  two  plantings  at  intermediate  dates.  Corn  from 
Diplodia-infected  seed  yielded  the  least  in  the  early  plantings  and  most  in 
the  late  plantings. 


300 


BULLETIN   No.   255 


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CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


301 


Dai-e  of 


Percent  field  stand 

10        ZO        30       -40       SO       60        70       80        90       100 


June  2 


Acre  y/e/d  fbu) 
10       20      30      40      50      60      JO      80      90 


May  4 


June  2 


^H  Sound  corn 

CHART  11.— YIELDS  FROM  GOOD  SEED,  SCUTELLUM-ROTTED  SEED,  AND 
FROM  DlPLODIA-lNFECTED  SEED  PLANTED  AT  THREE  DIFFERENT 
DATES  (Table  13  and  Chart  12) 

Altho  the  field  stands  of  corn  from  scutellum-rotted  seed  in- 
creased with  the  advance  in  the  date  of  planting,  the  yield  of  sound 
corn  from  such  seed  decreased  with  the  advance  in  date  of  planting. 
Both  field  stand  and  yield  of  sound  corn  from  Diplodia-infected 
seed  increased  with  the  advance  in  date  of  planting. 


302 


BULLETIN   No.   255 


[August, 


TAULE  13. — INFLUENCE  OF  DATE  OF  PLANTING  ON  FIELD  STAND  AND  YIELD  FROM 

GOOD  SEED,  FROM  DIPLODIA-!NFECTED  SEED,  AND  FROM  SEED  BADLY 

AFFECTED  WITH  SCUTELLUM  ROT 

Yellow  dent  corn  grown  on  brown  silt  loam,  Ontario  Parish,  near  Oneida,  1923 


Date 
of 
planting 

Character  of  seed 

Number 
of 
replications 

Field 
stand 

Acre  yield 

Total 

Sound 

May     4 

Good  

9 
6 
6 

perct. 
75.8  +  1.7 
47.5  +  1.9 
22.1  ±  1.5 

bu. 
66.1  +  1.6 
52.2  +  2.1 
26.6  ±  1.5 

bu. 

57.5  +  1.4 
43.3  +  2.2 
22.7  ±  1.5 

Scutellum-rotted 
Diplodia-infected 

May  14 

Good  

9 
6 
6 

89.8  +  1.2 
72.1  +  1.5 
34.3  ±  1.7 

71.9  +  1.7 
59.3  +  1.0 
38.6  ±  1.4 

59.2  +  1.9 
42.0  +  0.9 
32.5  ±  1.3 

Scutellum-rotted 
Diplodia-infected 

June     2 

Good  

9 
6 
6 

95.9  +  0.8 
89.3  +  1.1 
76.8  +  1.7 

68.6  +  1.6 
57.3  +  1.6 
56.3  ±  1.6 

55.9  +  2.4 
35.2  +  2.4 
45.7  +  2.4 

Scutellum-rotted 
Diplodia-infected 

PIG.     37.— SCUTEL- 

LUM-lNFECTED 

PLANTS  AFFECTED 

BY  DROUTH 
Note  curling  and 
dying  of  tips  of 
leaves  of  plants 
from  scutellum-rot- 
ted  seed  (right)  and 
healthy  appearance 
of  plants  from 
good  seed  (left) 
under  identical 
drouth  conditions. 
Planted  in  heavily 
infested  brown  silt 
loam,  near  Bloom- 
ington.  Corn  plants 
grown  from  infect- 
ed seed  or  from  a 
strain  susceptible 
to  root  rot  and  hav- 
ing partially  rotted 
root  systems  nearly 
always  suffer  first 
from  drouth. 


1924} 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


303 


TABLE  14. — MEAN  DAILY  SOIL  TEMPERATURES  AND  DAILY  RAINFALL 
FROM  MAY  6  TO  JUNE  11,  1923  (TAHLE  13) 

Soil  temperatures  taken  at  a  depth  of  four  inches,  Ontario  Parish,  near  Oneida 


Date 

Soil 
temperature 

Rainfall 

Date 

Soil 
temperature 

Rainfall 

May    6.  .  . 

°F. 
54  0 

inches 

May  26.  .  . 

°F. 
62.5 

inches 

7  

55  5 

27.. 

63  5 

8      .  . 

51  3 

05 

28 

64  5 

32 

9 

51  3 

29 

66  5 

10 

51  5 

30 

69  5 

11 

54  2 

1  90 

31 

69  5 

12 

53  9 

June    1 

73  0 

13 

52  6 

2 

73  3 

14  

52.0 

3..    . 

74.0 

15  

53  2 

4. 

74  0 

03 

16... 

54.1 

5.. 

74  0 

17  

54  9 

6 

73  5 

18  

55  7 

7 

71  5 

19  .... 

59  0 

8 

70  0 

20  .     . 

59  3 

9 

63  3 

21 

59  2 

31 

10 

63  5 

22  

58.9 

11   .      . 

(53  0 

52 

23 

58  5 

24  
25  

59.2 
60.5 

—  Mean  daily  so//,  temperature  at  4  inch  depth 

*  Dates  of  rainfall 

•  Inches  rain  fa  1 1  on  dates  indicated 


2.00 


.50 


6    7  8   9   10  II  12  13  14  15  16  IT  18  19  10  I/  12  ^3  24  fS  16  ?7&  193O3I  /    ?   3  4    56789/0/1 
May        it  t  *  June  *  * 

CHART   12. — SOIL  TEMPERATURES  AND  RAINFALL  AT  ONTARIO  PARISH,  1923 

(Table  14) 


304 


BULLETIN   No.   255 


[August, 


SOIL  MOISTURE  A  HIGHLY  IMPORTANT  FACTOR 

The  percentage  of  moisture  present  in  the  soil  frequently  is  the 
most  important  single  factor  influencing  the  behavior  of  diseased  or 
disease-susceptible  corn.  In  the  experiment  reported  in  Table  6,  high 
soil  moisture  probably  was  as  important  an  influencing  factor  as  tem- 
perature, especially  in  the  last  planting.  When  the  moisture  content 
is  below  optimum  for  plant  growth,  corn  plants  are  unable  to  carry 
on  their  normal  metabolism.  Corn  plants  grown  from  infected  seed 
or  from  a  strain  susceptible  to  root  rot  and  having  partially  rotted 


ao     90 


Good 
•seed 


Di/olodia- 

/nfected 

seed 


Moderate! u  /ow  so//  moisture 


Moderatetu  low  so/ I  moisture 


i-Sound 
'  corn 


Unsound 


corn 


Reduction  in  yield  of 
sound  corn  on  plots 
with  high  soil  moisture 


CHART  13. — YIELDS  FROM  DIPLODIA-INFECTED  SEED  PLANTED  UNDER  HIGH 
AND  UNDER  MODERATELY  LOW  SOIL  MOISTURE  CONDITIONS  (Table  15) 

Planting  at  a  time  of  high  soil  moisture,  as  compared  with  moderately 
low  soil  moisture,  results  in  greater  reductions  in  yields  of  sound  corn  from 
Diplodia-infected  seed  than  from  good  seed.  This  is  especially  true  under 
moderate  to  high  temperature  conditions. 

root  systems  are  the  first  to  suffer  from  the  ill  effects  of  a  drouth 
(Fig.  37).  On  the  other  hand,  strains  of  corn  resistant  to  root  rot, 
especially  resistant  strains  with  extensive  and  efficient  root  systems, 
may  not  be  affected  if  the  drouth  does  not  continue  too  long.  Under 
such  unfavorable  conditions  of  soil  moisture  as  frequently  obtain  dur- 
ing July  and  August,  differences  between  healthy  and  diseased  corn 
may  be  pronounced,  and  often  result  in  wide  differences  in  yield  of 
grain  at  the  end  of  the  season. 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


305 


TABLE  15. — INFLUENCE  OF  A  HIGH  AND  A  MODERATELY  Low  PERCENTAGE  OF  SOIL 

MOISTURE  DURING  THE  FIRST  TEN  DAYS  FOLLOWING  PLANTING,  ON  THE 

YIELD  OF  CORN  FROM  GOOD  SEED  AND  FROM  DIPLODIA-!NFECTED  SEED 

Yellow  dent  corn  planted  June  2,  1922,  on  brown  silt  loam  of  high  fertility, 

Bloomington 


Character  of  seed 

Number 
of 
plots 

Mean  acre  yields  on  plots 
with  — 

Reduction 
in  yield  on 
plots  with 
high  soil 
moisture 

Odds 

Moderately 
low  soil 
moisture 

High  soil 
moisture 

Total  Yield 


Good      

6 
6 

bu. 
88.5 
70.9 

bu. 

87.8 
56.5 

bu. 
0.7 
14.4 

1:1 
640:1 

Diplodia-infected  .  .  . 

Sound  Corn 

Good  

6 
6 

77.3 
62.6 

73.5 
48.3 

3.8 
14.3 

7:1 
219:1 

Diplodia-infected.  .  . 

Romyn,83  a  graduate  student  at  the  University  of  Illinois  in  1920- 
1922,  in  discussing  preliminary  trials  conducted  to  determine  the 
optimum  soil  moisture  for  growing  corn  in  pots  in  summer  at  a  tem- 
perature of  32°  to  37°  C.,  stated  that  "the  percentage  of  water  in  the 
disease-free  pots  can  be  reduced  to  40  percent  without  markedly 


Dry  Matter 

S  6!  * 

Percent 

of  Soil 

Moisture  of  Wet  and  Dry  Plots  Based  on  Dry  Soil 
Bloomington  Illinois  1922 

^ 

k^^ 

X*** 



X 

I 

^*^.. 

Percent  based  on 

^  rv>  r\>  C 
•»  Q  «  « 

'-'' 

\ 

/I 

\ 

^ 

>—  —  -=i 

V- 

At 

-f 

^ 

-^ 

'  . 

H? 

Days  -June  3  fc 
f/ot  Number  1- 
Plot  Number  Z~ 

Junt  14 
Dry 
Wet 

7  « 

Days  in  June 

CHART  14. — PERCENTAGE  OF  SOIL  MOISTURE  FROM  JUNE  3  TO  JUNE  14,  1922, 
BLOOMINGTON  (Table  15) 

affecting  the  yield,  but  a  decrease  to  40  percent  in  the  diseased  pots 
brings  about  a  distinct  decrease  in  yield. ' ' 

The  percentage  of  soil  moisture  present  at  planting  time  and  for 
the  first  week  or  ten  days  following  planting  may  be  the  most  impor- 
tant environing  factor  in  determining  the  extent  of  injury  in  corn 
grown  from  Diplodia-infected  seed,  at  least  where  the  soil  temperature 


306 


BULLETIN   No.   255 


[August, 


is  comparatively  high.  Data  bearing  on  this  relation  of  environment 
to  parasitism  by  Diplodia  are  given  in  Table  15  and  Chart  13.  These 
data  are  from  an  experiment  in  which  all  the  corn  was  planted  on  the 
same  day,  June  2,  1922.  The  following  day  half  of  the  plots  were 
watered  uniformly  with  a  hose.  They  were  kept  wet  by  frequent 
sprinklings  until  the  twelfth  day  after  planting,  when  there  was  a 
heavy  rain.  No  further  attempt  was  made  to  control  soil  moisture. 
Soil  moisture  and  temperature  records  for  the  period  are  presented  in 
Charts  14  and  15.  Differences  in  the  comparative  vigor  of  the  corn 
grown  from  good  seed  and  from  Diplodia-infected  seed  on  the  plots 
differing  in  soil  moisture  are  illustrated  in  Fig.  38.  Where  good  seed 
was  used  there  was  little  difference  in  total  yield  of  corn  from  the  wet 
and  the  dry  plots.  In  yield  of  sound  corn  the  difference  of  3.8  bushels 
in  favor  of  the  dry  plots  with  odds  of  7  to  1,  also  is  not  significant. 
However,  the  corn  grown  from  Diplodia-infected  seed  showed  a  re- 
duction of  14.4  bushels  per  acre  in  total  yield 'and  14.3  bushels  in 
yield  of  sound  corn,  with  odds  of  640  to  1  and  219  to  1,  respectively, 
on  the  plots  that  were  kept  wet  for  twelve  days  following  planting. 


Mean  Soil  Temperatures  of  Wet  and  Dry  Plots     Bloom ington.  Illinois 


JS 


CHART  15. — SOIL  TEMPERATURES  FROM  JUNE  3  TO  JUNE  15,  1922,  BLOOMINGTON 

(Table  15) 

In  general  it  may  be  said  that  planting  at  a  time  of  high  soil 
moisture,  as  compared  with  moderately  low  soil  moisture,  results  in 
greater  reductions  in  yield  of  sound  corn  from  Diplodia-infected  seed 
than  from  good  seed.  This  is  especially  true  under  moderate  to  high 
temperature  conditions. 


1924} 


COSN  BOOT,  STALK,  AND  EAR  EOT  DISEASES 


307 


FIVE  lOiS  PLAMTEDlllliPLOWAUffECIi  SEED 


TIG.  38. — EFFECT  OF  SOIL  MOISTURE  ON  DIPLODIA  INJURY 

Corn  from  good  seed  (left)  and  from  Diplodia-infected  seed  (right) 
on  plots  differing  widely  in  soil  moisture  for  the  first  twelve  days  following 
planting,  near  Bloomington.  Note  the  greatly  reduced  stand  and  reduced 
vigor  of  corn  from  Diplodia-infected  seed  on  the  plots  with  high  soil 
moisture  content.  Where  good  seed  was  used  there  was  little  difference  in 
total  yield  of  corn  from  the  wet  and  the  dry  plots. 


INFLUENCE    OF   SOIL  AERATION 

It  is  a  well  established  fact  that  aeration  is  essential  to  the  produc- 
tivity of  the  soil.  Lack  of  aeration,  usually  following  imperfect  drain- 
age and  poor  cultivation,  results  in  the  accumulation  of  carbon  dioxid 
and  the  formation  of  reductive  fermentation.  Such  conditions  usually 
are  injurious  to  corn  plants,  particularly  if  they  continue  long  enough 


308 


BULLETIN   No.   255 


[August, 


TABLE  16. — INFLUENCE  OP  SOIL  AERATION  ON  GROWTH  OF  PLANTS  FROM 
GOOD  SEED  AND  FROM  FUSARIUM-!NFECTED  SEED1 

Yellow  dent  corn  grown  in  pots,  Urbana,  1922 


Frequency 
of 
aeration 

Character  of  seed 

Number 
of 
pots 

Mean 
total 
air-dry 
weight 
of  plants 

Difference  in  weight 
of  plants  grown  from 
good  seed  and  from 
Fusarium-infected 
seed 

Daily  

Good  

4 

4 

4 
4 

4 
4 

4 
4 

4 
4 

gms. 
8.00 
7.51 

10.11 
5.73 

9.01 
4.17 

8.68 
3.81    ,, 

9.74 
2.84 

gms. 
0.49 

4.38 
4.84 
4.87 
6.90 

perct. 
6.1 

43.3 
53.7 
56.1 

70.8 

Every  2  days 
Every  4  days 
Every  8  days 
None  

Fusarium-infected  .  .  .  . 
Good  

Fusarium-infected  .... 
Good  

Fusarium-infected  .... 
Good  

Fusarium-infected  .... 
Good  

Fusarium-infected  .... 

1  Unpublished  data  of  E.  A.  Romyn,  University  of  Illinois. 


Frequency 
of  aeration 

Daily 


Every 
two  days 

Every  \ 

four  days 

Every  I 

eight  days\ 


None 


Mean  total  air- dry  weight  (grams) 

0/23456789          10        II 


Good  seed 


•  Fusarium-infected  seed 


Good  seed 


Good  seed 


Good  seed 


Good  seed 


CHART  16. — FUSARIUM  INJURY  AS  AFFECTED  BY  SOIL  AERATION  (Table  16) 

Corn  from  Fusarium-infected  seed  was  affected  adversely  by  a  lack  of 
frequent  aeration,  whereas  corn  from  good  seed  was  not  injured  by  the  same 
unfavorable  conditions. 


1984]  CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES  309 

to  form  a  metallic  solution  of  ferrous  compounds,38  which  are  very 
toxic  and  "are  commonly  regarded  as  one  cause  of  the  sterility  of 
badly  aerated  soils.  "86>page84  Corn  grown  from  infected  and  disease- 
susceptible  seed  is  the  first  to  be  injured  by  such  unfavorable  condi- 
tions. However,  if  the  lack  of  drainage  and  aeration  persist,  the 
disease  resistance  of  corn  from  good  seed  also  may  be  broken  down. 
Proper  soil  aeration  not  only  facilitates  the  complete  oxidation  of  only 
partially  oxidized  substances  in  the  soil  that  may  be  toxic,  especially 
to  corn  plants  from  infected  seed  and  to  plants  very  susceptible  to 
injury  under  such  conditions,  but  also  aids  in  preventing  the  forma- 
tion of  such  substances. 

Romyn,83  working  with  good  seed  and  Fusarium-infected  seed, 
grew  plants  in  sealed  pots  in  a  greenhouse  maintained  at  a  temperature 
of  20°  to  21°  C.  The  pots,  containing  sand  and  a  nutrient  solution, 
were  divided  into  series  which  were  aerated  at  intervals  of  twenty- 
four  hours,  two  days,  four  days,  and  eight  days,  respectively.  One 
series  received  no  aeration.  Summarized  data  from  two  experiments 
conducted  at  different  dates  are  given  in  Table  16  and  Chart  16. 
Romyn  comments  as  follows : 

"It  appears  that  once  a  pot  is  sealed,  the  amount  of  artificial  aeration 
it  receives  makes  no  significant  difference  in  the  yield  of  plants.  In  both 
experiments  the  disease-free  plants  receiving  no  aeration  yielded  as  well 
as  those  aerated  daily. 

"The  amount  of  aeration  does,  however,  make  a  difference  in  the  de- 
velopment of  the  fungus.  The  progressively  decreasing  yields  of  diseased 
corn  with  the  fewer  aerations  can  be  attributed  to  an  increasing  virulence 
of  the  disease.  Tho  the  plants  in  the  frequently  aerated  pots  also  were 
diseased,  they  grew  more  vigorously,  while  the  progress  of  the  pathogene 
was  retarded." 

These  interesting  data  (Table  16)  contribute  to  a  proper  interpre- 
tation of  the  field  performance  of  corn  grown  from  good  seed  and  from 
diseased  seed  on  soil  poorly  drained  and  hence  poorly  aerated. 

EFFECT   OF  AMOUNT   OF  PLANT-FOOD    MATERIALS  IN   SOIL  SOLUTION 

That  it  is  important  to  maintain  the  permanent  fertility  of  the 
soil  is  an  established  fact.  A  lack  of  any  of  the  essential  plant-food 
materials  is  certain  to  result  in  a  decreased  yield.  Altho  the  prob- 
lems of  soil  fertility  and  corn  diseases  are  closely  interrelated,  they 
constitute  two  distinct  groups  of  problems.  The  soil  fertility  problem 
obviously  cannot  be  solved  by  seed  selection  and  breeding  alone; 
neither  can  the  corn  disease  problem  be  controlled  entirely  by  soil 
treatment  and  soil  management. 

The  significance  of  this  situation  can  better  be  appreciated  by  a 
careful  study  of  the  data  presented  in  Table  17.  It  will  be  observed 


310  BULLETIN  No.   255  [August, 

that  there  is  a  substantial  and  consistent  increase  in  yield  on  the  plots 
where  manure,  limestone,  and  rock  phosphate  have  been  applied.  Yet 
in  spite  of  the  fact  that  the  majority  of  these  treated  plots  represent 
the  best  soil  treatment  and  soil  management  known  at  the  present 
time  on  farms  in  central  Illinois,  there  is  a  significant  difference  in 
yield  between  the  corn  grown  from  good  seed  and  that  grown  from 
diseased  seed  of  the  same  strain  under  what  would  ordinarily  be 
termed  the  most  favorable  soil  conditions.  Altho  certain  of  the  corn 
rot  diseases  may  be  controlled  largely  by  soil  treatments,  there  are 
other  corn  rot  diseases  the  injury  from  which  is  lessened  only  slightly 
by  the  same  treatments.  As  would  be  expected,  the  highest  average 
yields  were  obtained  with  good  seed  on  properly  treated  soil.  The 
average  yield  of  corn  from  diseased  seed  on  the  treated  plots  was  only 
slightly  better  than  the  yield  of  corn  from  good  seed  on  the  no- 
treatment  plots,  66.7  bushels  per  acre  compared  with  66.2  bushels. 

For  a  soil  to  be  productive  it  is  necessary  not  only  that  the  soil 
solution  should  contain  all  the  essential  plant-food  materials,  but  that 
all  necessary  nutrients  should  be  present  in  their  proper  proportion, 
a  condition  which  has  been  designated  as  "physiological  balance." 
An  excess  of  some  one  plant-food  material  may  be  as  detrimental  as  a 
deficiency.  Following  is  a  discussion  of  these  various  elements  of  the 
soil  and  the  part  that  each  plays  in  plant  nutrition. 

Nitrogen  Excess  or  Deficiency 

Altho  an  excess  of  nitrogen  seldom  is  a  serious  problem  on  the 
farms  of  the  corn  belt,  there  is  experimental  evidence  that  too  much 
nitrogen  favors  the  development  of  at  least  two  of  the  corn  rot  diseases. 
Nitrogen  starvation  causes  a  marked  stunting  and  a  yellowing  of  the 
entire  foliage.  A  deficiency  of  this  element  is  so  common  an  occur- 
rence that  it  presents  one  of  the  greatest  problems  in  American  agri- 
culture. 

Importance  of  Phosphorus 

The  importance  of  the  element  phosphorus  in  plant  nutrition  has 
received  much  attention.  Thatcher103  makes  the  following  sum- 
marized statement : 

"Abundance  of  available  phosphorus  early  in  the  plant's  life  greatly 
stimulates  root  growth,  and  later  on  it  undoubtedly  hastens  the  ripening 
process;  hence  this  element  seems  to  act  as  the  exact  antithesis  of 
nitrogen. ' ' 

Large  areas  of  Illinois  soils  are  deficient  in  phosphates,  and  the  ap- 
plication of  phosphates  on  such  soils,  together  with  proper  soil  man- 
agement, has  been  found  to  result  in  increased  yields  of  improved 
quality. 

Corn  grown  from  good  seed  and  from  infected  seed  differs 
greatly  in  its  response  to  an  increase  of  available  phosphates  in  the 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


311 


TABLE  17. — INFLUENCE  OF  MANURE,  LIMESTONE,  AND  ROCK  PHOSPHATE  ON  YIELD 
FROM  GOOD  SEED  AND  FROM  VARIOUS  LOTS  OF  DISEASED  SEED 

Brown  silt  loam  on  various  fields  in  Illinois,  1919-1922 


Year 

Location 
(Illinois) 

Character  of  seed 

Acre  yield 

No 

treatment 

Manure, 
limestone, 
rock 
phosphate 

1919 
1920 
1920 
1920 
1920 
1920 
1921 
1921 
1921 
1921 
1921 
1921 
1921 
1922 
1922 
1922 
1922 
1922 
1922 
1922 
1922 

Urbana  

Good  

bu. 
70.4 
56.6 
76.1 
47.4 
77.0 
55.6 
85.7 
69.7 
103.8 
60.7 

bu. 
97.4 
84.2 
77.0 
63.8 
80.1 
66.5 
91.7 
75.5 
110.4 
90.3 
80.8 
68.1 
100.7 
90  9 
90.5 
77.0 
74.7 
57.7 
75.2 
60.9 
74.1 
51.5 
77.5 
70.8 
74.1 
66.5 
100.0 
95.6 
59.2 
57.5 
56.1 
44.7 
67.1 
44.0 
39.3 
38.2 
71.5 
68.7 
75.6 
77.3 
58.3 
51.5 

Bloomington  . 

Scutellum-rotted  

Good  

Bloomington 

Scutellum-rotted  

Good  

Bloomington  

Scutellum-rotted  

Good  

Urbana  

Scutellum-rotted  

Good  

Urbana   

Diplodia-infected  

Good  

Urbana  

Scutellum-rotted  

Good  

Urbana  

Scutellum-rotted  

Good  

Bloomington  

Scutellum-rotted  

Good  

64.3 
57.2 
64.4 
57.9 
67.4 
53.0 
65.7 
58.5 
67.4 
60.6 

Bloomington  ...    . 

Scutellum-rotted  

Good  

Bloomington  

Scutellum-rotted 

Good  

Bloomington  

Diplodia-infected  

Good  

Bloomington  

Fusarium-infected  

Good  

Jloomington  

Fusarium-i  nf  ected 

Good  

Jrbana  

Scutellum-rotted  

Good  

Urbana  

Scutellum-rotted  

Good  

Urbana  

Scutellum-rotted  

Good  

61.7 
39.5 
25.8 
22.9 
48.7 
49.8 
49.0 
44.5 

Urbana  

Diplodia-infected 

Good  

Urbana  

Fusarium-infected  

Good  

Urbana  

Fusarium-infected  

Good  

Urbana  

^usarium-infected  

Good  . 

^usarium-infected  

Grand  average  

Good  

66.2 
52.4 

77.7 
66.7 

Diseased  

312 


BULLETIN   No.   255 


[August, 


TABLE  18. — INFLUENCE  OF  ROCK  PHOSPHATE  ON  YIELD  FROM  GOOD  SEED 
AND  FROM  FUSARIUM-INFECTED  SEED 

Yellow  dent  corn  grown  on  brown  silt  loam,  part  of  the  plots  receiving  organic 
manure  only  and  part  receiving  organic  manure  and  rock  phosphate,  North-Central 
and  South-Central  rotations,  University  South  Farm,  1922 


Rotation 

Character  of  seed 

Acre  yield 
on  plots 
receiving 
organic 
manure 

Effect  of  rock  phosphate 
in  addition  to  organic 
manure 

Increase          Decrease 

Total  Yield 


Corn,  corn,  spring 

Good  

bu. 
59  6 

bu. 
2  4 

bu. 

grains,  clover.  .  .  . 
Corn,    corn,    corn, 

Fusarium-infected  .  . 
Good  

50.8 
35.0 

12.0 
4.9 

soybeans  

Fusarium-infected.  . 

30.5 

7.3 

Sound  Corn 


Corn,  corn,  spring 

Good  

bu. 
49.3 

bu. 
4.3 

bu. 

grains,  clover.  .  .  . 
Corn,    corn,    corn, 

Fusarium-infected.  . 
Good  

37.7 

27  6 

18.4 
6  3 

soybeans  

Fusarium-infected.  . 

21.1 

10.4 

soil,  the  increase  in  yield  of  corn  from  Fusarium-infected  seed  being 
much  greater  than  the  increase  from  good  seed.  Typical  examples  of 
such  increases  are  shown  in  Tables  18  and  19  and  Chart  17.  The 
yields  of  sound  corn  from  the  Fusarium-infected  seed  reported  in 
Table  18  were  increased  18.4  and  10.4  bushels  per  acre,  respectively, 
in  the  two  rotations,  by  the  application  of  rock  phosphate,  while  the 
yields  from  good  seed  were  increased  only  4.3  and  6.3  bushels,  re- 
spectively. The  following  year  on  the  same  plots  (Table  19)  the  acre 
yield  of  sound  corn  from  Fusarium-infected  seed  was  increased  from 
43.5  bushels  on  the  plots  receiving  manure  only  to  49.3  bushels  on  the 
phosphated  plots,  or  an  increase  of  5.8  bushels.  The  acre  yield  of 
sound  corn  from  good  seed  was  increased  only  0.7  bushel  by  the  same 
treatment.  On  the  plots  receiving  organic  manure  only,  corn  from 
Fusarium-infected  seed  yielded  8.0  bushels  less,  with  odds  greater 
than  9999  to  1,  than  corn  from  good  seed,  while  on  the  plots  receiv- 
ing rock  phosphate  the  difference  in  yield  was  only  2.9  bushels,  with 
odds  of  39  to  1. 

Data  in  Table  20  also  show  that  disease-susceptible  corn  on  phos- 
phated soil  apparently  may  be  highly  resistant  to  the  particular  dis- 
ease under  experimentation  and  may  yield  approximately  as  much  as 
a  good-seed  selection.  On  adjacent  plots  where  the  supply  of  available 
phosphates  is  less  the  decrease  in  yield  may  be  very  pronounced. 


CORN  BOOT,  STALK,  AND  EAR  HOT  DISEASES 


313 


TABLE  19. — INFLUENCE  OF  ROCK  PHOSPHATE  ON  YIELD  FROM  GOOD  SEED 
AND  FROM  FUSARIUM-INFECTED  SEED 

Yellow  dent  corn  planted  May  14,  1923,  on  brown  silt  loam,  part  of  the  plots 
receiving  organic  manure  only  and  part  receiving  manure  and  rock  phosphate, 
North-Central  and  South-Central  rotations,  University  South  Farm,  Urbana 


Soil 
treatment 

Character 
of  seed 

Number 
of 
replica- 
tions 

Mean  acre 
yield 

Reduction  in 
sound  corn  fol- 
lowing use  of 
Fusarium-infected 
seed 

Odds 

Total 

Sound 

bu. 

bu. 

bu. 

perct. 

Organic  manure 

Good  seed. 

16 

•  59.1 

51.5 

Fusarium- 

infected  . 

16 

51.5 

43.5 

8.0 

15.5  >  9999:1 

Organic  manure 

Good  seed  . 

16 

60.1 

52.2 

and  rock  phos- 

Fusarium- 

phate  

infected  . 

16 

56.1 

49.3 

2.9 

5.6 

39:1 

The  effects  of  applications  of  phosphate  on  the  yields  of  corn 
grown  from  good  and  from  infected  seed  are  not  always  so  pro- 
nounced as  the  data  in  Tables  18,  19,  and  20  would  seem  to  indicate, 
even  on  soils  of  the  same  general  type  and  of  apparently  equal  fer- 
tility. Data  from  forty-two  experiments  located  on  brown  silt  loam 
at  various  points  in  central  Illinois  and  covering  a  period  of  two  years 
are  summarized  in  Table  21.  It  will  be  observed  that  corn  from  good 
seed  did  not  always  give  a  significant  increase  in  yield  on  the  phos- 
phated  plots.  Obviously,  in  many  instances,  the  corn  from  good  seed, 
with  its  extensive  healthy  root  systems,  was  able  to  get  a  sufficient 
supply  of  phosphates  from  the  soil  that  received  no  additional  phos- 

TABLE  20. — INFLUENCE  OF  ROCK  PHOSPHATE  ON  YIELD  FROM  GOOD  SEED 
AND  FROM  DISEASE-SUSCEPTIBLE  SEED 

Yellow  dent  corn  grown  on  infested  brown  silt  loam,  part  of  the  plots  receiving 
limestone  only  and  part  receiving  both  limestone  and  rock  phosphate,  near  Bloom- 
ington,  1920. 


Character  of  seed 

Yield  of  plots 
receiving 
limestone  only 

Effect  of  rock  phosphate  in 
addition  to  limestone 

Increase 

Decrease 

Total  Yield 


Good  

bu. 
81  3 

bu. 

bu. 
0.3 

Disease-susceptible  

70.6 

6.9 

Sound  Corn 


Good  

bu. 
76.1 

bu. 
0.9 

Disease-susceptible  

65.0 

8.4 

314 


BULLETIN   No.   255 


phates.  In  interpreting  the  responses  of  healthy  corn  to  application 
of  phosphate,  differences  in  various  strains  of  corn  should  be  con- 
sidered. There  is  evidence  that  certain  strains,  on  account  of  their 
extensive  and  fibrous  root  systems,  are  more  efficient  in  utilizing  lim- 
ited supplies  of  this  plant-food  element  than  other  strains  that  appear 
equally  healthy. 


Soil 


Organic 
manure 


Organic 
manure  and 
rock 
phosphate 


Mean  acre  yield    (bu.) 
30          40          50 


Goodseec 

— ^—^— • 
Fusari urn-infected 


Difference 

^^|  Sound  corn' 
i 

CHART  17. — YIELDS  FROM  FUSARIUM  SEED  AS  INFLUENCED 

BY  PHOSPHATES  (Table  19) 

The  yield  of  corn  grown  from  Fusarium-infected  seed 
is  greatly  increased  by  an  application  of  phosphate  to  the 
soil. 

The  ability  of  corn  from  good  seed  to  respond  favorably  to 
applications  of  phosphate  is  further  conditioned  by  date  of  planting 
and  other  important  factors  which  are  not  within  the  province  of  the 
present  bulletin. 

Corn  grown  from  scutellum-rotted  seed  was  benefited  more  by  the 
application  of  phosphate  than  was  corn  from  good  seed.  The  acre 
yield  of  sound  corn  from  good  seed  was  increased  3.5  bushels,  with 
odds  of  only  18  to  1,  while  under  the  same  conditions  the  yield  of 
sound  corn  from  scutellum-rotted  seed  was  increased  6.6  bushels,  with 
odds  of  69  to  1,  which  are  significant  from  the  standpoint  of  odds  of 
probability. 

Altho  there  were  instances  where  corn  grown  from  Diplodia- 
infected  seed  was  benefited  markedly  by  applications  of  phosphate, 
there  were  other  instances  where  the  virulence  of  the  disease  ap- 
parently was  increased  by  the  same  treatment,  a  typical  example  of 
which  is  given  in  Table  22.  In  the  planting  on  May  8  there  was  a 
substantial  increase  in  the  yield  of  corn  from  Diplodia-infected  seed 
on  the  phosphated  plot,  but  in  the  later  plantings  there  were  slight 
decreases.  Thus,  on  the  whole,  injury  and  loss  in  either  total  yield 


CORN  BOOT,  STALK,  AND  EAR  HOT  DISEASES 


315 


TABLE  21. — SUMMARY  OF  DATA  SHOWING  THE  INFLUENCE  OF  ROCK  PHOSPHATE  ON 

YIELD  FROM  GOOD  SEED  AND  FROM  VARIOUS  LOTS  OF  DISEASED  SEED 
Corn  grown  on  brown  silt  loam  at  various  points  in  central  Illinois,  1921,  1922 


Years 
represented 

Number  of 
counties 
represented 

Number  of 
experiments 
represented 

Character  of  seed 

Acre  yield 

Increase 
on 
phos- 
phated 
plots 

Odds 

No 
treat- 
ment 

Phos- 
phated 

Total  Yield 


2 

4 

13 

Good 

bu. 
59  6 

bu. 
63  9 

bu. 
4  3 

62:1 

(1921-22) 
2 

4 

10 

Scutellum-rotted  .  . 
Good  

51.4 
57.9 

56.0 
61.3 

4.6 
3.4 

65:1 
22:1 

(1921-22) 
2 

4 

10 

Diplodia-infected  .  . 
Good 

39.7 
58  1 

43.2 
59  4 

3.5 
1.3 

10:1 
4:1 

(1921-22) 
1 

2 

9 

Fusarium-infected  . 
Good  

48.9 
63.4 

54.1 
65.0 

5.2 
1.6 

1427:1 
3:1 

(1922) 

Starchy  

53.8 

61.1 

7.3 

384:1 

Sound  Corn 

2 

4 

13 

Good  

50  4 

53.9 

3.5 

18:1 

(1921-22) 
2 

4 

10 

Scutellum-rotted  .  . 
Good    

41.0 
49  1 

47  6 
53  8 

6.6 
4.7 

69:1 
41:1 

(1921-22) 
2 

4 

10 

Diplodia-infected.  . 
Good  

32.6 
50.4 

.36.9 
52.6 

4.3 

2.2 

10:1 
10:1 

(1921-22) 
1 

2 

9 

Fusarium-infected  . 
Good  

40.1 
52  4 

47.8 
57  7 

7.7 
5.3 

1110:1 
3332:1 

(1922) 

Starchy  

43.0 

49.2 

6.2 

109:1 

TABLE  22. — INFLUENCE  OF  ROCK  PHOSPHATE  ON  YIELD  FROM  GOOD  SEED 
AND  FROM  DIPLODIA-INFECTED  SEED 

Yollow  dent  corn  grown  on  brown  silt  loam,  part  of  the  plots  receiving  no  treat- 
ment and  others  receiving  rock  phosphate,  Ontario  Parish,  near  Oneida,  1922 


Date  of 
planting 

Character  of  seed 

Acre  yield  of 
sound  corn 
on  no-treat- 
ment plots 

Effect  of  rock  phosphate 
on  yield  of  sound  corn 

Increase 

Decrease 

May    8  

Good  

bu. 
69.8 
50.2 

72.8 
53.9 

68.3 
54.0 

bu. 
13.0 

bu. 
2.6 

4.1 
4.9 

0.2 
4.5 

May  16  

Diplodia-infected  

Good  

May  29  

Diplodia-infected  

Good  

Diplodia-infected  

316  BULLETIN  No.   255  [August, 

or  yield  of  sound  corn  from  Diplodia-infected  seed  were  not  signifi- 
cantly reduced  by  applications  of  phosphate  (Table  21). 

Data  obtained  up  to  the  present  time  indicate  that  lack  of  abun- 
dance of  available  phosphates  may  be  an  important  predisposing 
factor  with  corn  grown  from  Fusarium-infected  seed.  In  the  case  of 
corn  from  good  seed  in  this  particular  series  of  experiments  (Table 
21),  neither  the  total  yield  nor  the  yield  of  sound  corn  was  increased 
appreciably  by  applications  of  phosphate,  the  increases  being  only 
1.3  and  2.2  bushels  per  acre,  respectively.  On  the  other  hand,  both 
total  yields  and  yields  of  sound  corn  from  Fusarium-infected  seed 
from  the  same  strains  of  corn  were  significantly  increased,  the  in- 
creases being  5.2  and  7.7  bushels  per  acre,  respectively,  with  markedly 
high  odds  of  probability  in  each  case. 

Since  kernel  starchiness  indicates  susceptibility  to  the  corn  rot 
diseases,  as  will  be  developed  later  in  this  bulletin,  the  response  of  corn 
from  such  seed  to  applications  of  phosphate  is  very  suggestive  (Table 
21).  Total  yield  of  corn  from  good  seed  was  increased  only  1.6 
bushels  per  acre  on  the  phosphated  plots,  with  odds  of  only  3  to  1, 
while  the  total  yield  of  corn  from  starchy  seed  in  the  same  test  was 
increased  7.3  bushels,  with  odds  of  384  to  1. 

The  results  of  Romyn,83  from  pot  experiments  conducted  with  the 
same  seed  lots  that  were  used  in  experiments  reported  in  Tables  18 
and  19,  seem  to  indicate  that  corn  from  Fusarium-infected  seed  may 
require  more  phosphate  than  is  required  by  corn  from  good  seed.  In 
determining  the  hydrogen-ion  concentration  of  the  nutrient  solution 
in  the  pots,  Romyn  found  that  the  pots  containing  plants  from 
Fusarium-infected  seed  were  a  little  less  acid  than  those  growing 
plants  from  good  seed.  This  difference  also  was  brought  out  by 
comparing  in  like  manner  the  nutrient  solutions  in  pots  containing 
plants  grown  from  good  seed,  but  in  a  number  of  which  some  of  the 
plants  were  diseased.  In  general  the  nutrient  solutions  in  the  pots 
containing  the  greatest  number  of  diseased  plants  were  less  acid  in 
reaction  than  those  containing  few  or  no  diseased  plants.  A  summary 
of  Komyn's  results  is  presented  in  Table  23.  His  comments  and  in- 
terpretation are  as  follows: 

"Altho  the  data  are  limited,  they  seem  to  indicate  a  larger  absorption 
of  the  anions,  or  acid  radicals,  in  the  nutrient  solution  by  the  diseased 
corn.  The  possibility  that  this  difference  in  hydrogen-ion  concentration  is 
due  to  a  larger  excretion  of  carbon  dioxid  by  the  good  seed  roots  can  be 
dismissed  for  two  reasons.  In  the  first  place,  any  accumulation  of  carbon 
dioxid  in  the  pots  would  have  diminished  the  root  growth  in  those  pots  in 
Experiments  4  and  5  which  were  aerated  only  at  long  intervals — this  did 
not  happen.  Clements,12  in  a  recent  symposium  on  aeration,  summarizes 
the  work  of  a  number  of  investigators  which  supports  this  contention. 
Secondly,  the  sweep  of  air  thru  the  pots  in  the  taking  of  the  samples 


1984} 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


317 


TABLE    23. — INFLUENCE  OF  PLANTS  FROM  GOOD  SEED  AND  FROM  FUSARIUM-!N 
FECTED  SEED  ON  THE  HYDROGEN-ION  CONCENTRATION  OF  THE  SOIL  SOLUTION  l 

Yellow  dent  corn  grown  in  pots,  Urbana,  1922 


Difference  in  PH 

Mean 

value  between 

Lime 
treatment 

Character  of  seed 

Number 
of 

hydrogen-ion 
concentration 

pots  containing 
corn  from  good 

Odds 

pots 

in  PH  values 

and  from  in- 

fected seed 

None  

Good    

11 

5  622 

Fusarium-infected  .  .  . 

11 

5.737 

0.115 

107:1 

Limed  

Good  

11 

5.866 

Fusarium-infected.  .  . 

11 

5.943 

0.077 

25:1 

Unpublished  data  of  E.  A.  Romyn,  University  of  Illinois. 

would  probably  have  equalized  the  carbon  dioxid  saturation  in  all  the  so- 
lutions drawn  off. 

"It  is  not  possible  to  say  which  of  the  anions  has  been  absorbed,  but 
as  the  acidity  of  the  solution  is  due  to  the  H2P04  ion  of  the  KH2P04,  it 
seems  very  likely  that  this  ion  has  been  absorbed  for  the  purpose  of  sup- 
plying either  extra  P  or  an  acid  radical  to  the  diseased  plants. 

' '  In  interpreting  these  results,  the  effect  of  the  sand  itself  on  the  pH  of 
the  nutrient  solution  should  be  taken  into  account.  Both  Shive93  and 
Hoagland39  have  reported  that  the  hydrogen-ion  concentration  of  a  nutrient 
solution  is  markedly  affected  by  the  addition  of  quartz  sand.  Both  these 
workers,  however,  washed  their  sand  carefully  (Hoagland  taking  the 
further  precaution  of  treating  the  sand  with  HCL)  and  thoroly  flooded  the 
sand  at  each  change  of  nutrient  solution.  The  sand  in  this  experiment  was 
not  washed  or  so  extensively  irrigated  and  an  effect  of  some  alkaline  re- 
acting materials  was  noticed.  But  as  this  initial  effect  would  be  practically 
overcome  by  the  end  of  the  growth  period  and  would  affect  both  strains  in 
the  same  way,  it  does  not  interfere  with  the  comparative  value  of  the 
hydrogen-ion  concentration  of  the  final  solutions  drawn  off." 

The  data  of  Tables  15  to  20  indicate  not  only  that  a  lack  of  an 
abundant  phosphate  supply  may  be  an  important  factor  predisposing 
corn  to  disease,  but  also  that  seed  infection  and  seed  condition  are 
factors  that  deserve  careful  attention  in  studying  any  physiological 
problem  relating  to  phosphate  nutrition  of  corn. 

Potassium  and  Disease  Susceptibility 

Thatcher103  summarizes  the  role  of  potassium  in  plant  nutrition 
as  follows : 

"The  popular  expression  that  'potash  makes  sugars  and  starch'  is  a 
surprisingly  accurate  description  of  the  role  of  this  element  in  plant 
metabolism.  Either  the  photosynthesis  of  starch,  or  the  changes  necessary 
to  its  translocation  (it  is  not  yet  certain  which)  is  so  dependent  upon  the 
presence  of  potassium  in  the  cell  sap  that  the  whole  process  stops  at  once 


318 


BULLETIN   No.   255 


[August, 


if  an  insufficient  supply  is  present.  ...  The  grains  of  the  cereal  crops 
become  shrunken  as  a  result  of  potassium  starvation;  and  are  plump  and 
well-filled  with  starch  in  the  endosperm  when  sufficient  potassium  is  avail- 
able for  the  crop's  needs." 

The  relation  of  potassium  starvation  to  disease  susceptibility  has 
been  studied  by  a  number  of  investigators.  Russell86  summarizes  the 
results  at  Rothamsted  as  follows :  ' '  The  vigor  and  healthiness  of  the 
plant  are  the  first  to  suffer  in  a  bad  season,  or  to  succumb  to  disease. ' ' 

TABLE  24. — SUMMARY  OF  DATA  SHOWING  THE  INFLUENCE  OF  POTASSIUM  SULFATE 

ON  YIELD  FROM  GOOD  SEED  AND  FROM  VARIOUS  LOTS  OF 

DISEASED  AND  DISEASE-SUSCEPTIBLE  SEED 

Grown  on  brown  silt  loam  of  medium  fertility.  Bloomington,  1923 


Number 
of 
experi- 
ments 

Character  of  seed 

Acre  yield 

Increase  on 
potassium 
sulfate 
plots 

Odds 

No 

treatment 

Treated 

with 
potassium 
sulfate 

Total  Yield 


4 

Good  

bu. 
67.0 

bu. 
68.0 

bu. 
1.0 

3:1 

4 

Scutellum-rotted  

62.0 

66.2 

4.2 

9:1 

4 

Diplodia-infected  

51.4 

48.7 

-2.7 

5:1 

4 

Fusarium-infected  

64.1 

66.9 

2.8 

3:1 

Sound  Corn 


4 

Good  

46  2 

46.6 

0.4 

1:1 

4 

Scutellum-rotted 

30  2 

39.1 

8.9 

141:1 

4 

Diplodia-infected  

31.5 

34.2 

2.7 

11:1 

4 

Fusarium-infected  

38.9 

49.4 

10.5 

66:1 

Data  showing  the  effect  of  applications  of  potassium  sulfate  on  the 
yield  of  corn  grown  from  good  seed  and  from  diseased  seed  are  given 
in  Table  24.  The  soil  on  which  this  experiment  was  located  had  not 
grown  a  leguminous  crop  for  several  years.  The  supply  of  decaying 
organic  matter  was  rather  low.  Under  such  conditions  a  deficiency 
of  available  potassium  salts  might  exist.  Corn  from  good  seed  was 
not  affected  either  in  total  yield  or  in  yield  of  sound  corn  by  applica- 
tions of  potassium  sulfate.  However,  the  quality  of  the  yield  from 
both  scutellum-rotted  and  Fusarium-infected  seed  was  significantly 
improved,  the  increases  in  sound  corn  being  8.9  and  10.5  bushels  per 
acre,  with  odds  of  141  to  1,  and  66  to  1,  respectively.  Corn  from 
Diplodia-infected  seed  apparently  was  not  benefited  in  any  way  by  the 
same  applications  of  potassium  sulfate.  In  other  soil  experiments 
where  the  soil  was  well  supplied  with  decaying  organic  matter  and 
available  phosphates,  no  such  benefits  from  the  addition  of  potassium 
salts  were  observed. 


1!)%4]  CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES  319 

INJURIOUS    CONSTITUENTS  IN   SOIL   SOLUTION 

Toxic  Substances 

The  problem  of  organic  and  inorganic  constituents  in  the  soil 
which  are  injurious  to  plants  has  received  much  attention,  both  in  the 
United  States  and  in  other  countries.  There  seems  to  be  fairly  con- 
clusive evidence  that  toxic  substances  may  form  in  poorly  drained  and 
poorly  aerated  soils  and  in  soils  lacking  calcium  carbonate,  or  lime. 
The  active  agencies  in  producing  so-called  "sour"  or  "acid"  soils 
have  been  the  subject  of  much  study.  The  toxic  properties  of  acid 
soils  may  result  either  from  the  presence  of  true  acids  in  the  soil  or 
from  a  lack  of  basicity.86  In  the  latter  case  soluble  aluminum  and  fer- 
rous salts,  and  in  certain  instances  manganese,  are  believed  to  be 
largely  responsible  for  the  toxic  effect  of  such  soils  upon  plant  growth. 

Soluble  aluminum  compounds  do  not  form  readily  in  soils  well 
supplied  with  lime  and  available  phosphates.  Moreover,  applications 
of  limestone  in  proper  amounts  change  these  soluble  compounds  into 
insoluble  and  non-acid  forms.  Connor13  and  others  expressed  the  be- 
lief that  the  beneficial  effects  of  applications  of  available  phosphates 
are  due  as  much  to  their  rendering  the  aluminum  salts  insoluble  as 
to  the  extra  supply  of  available  phosphate  they  furnish. 

Hoffer  and  Carr42  found  that  root  rots  of  corn  were  more  severe 
' '  in  soils  notable  for  their  deficiencies  in  lime  and  available  phosphates 
than  in  other  soils,"  and  showed  that  the  absorption  and  accumula- 
tion of  iron  and  aluminum  salts  in  the  nodal  tissues  resulted  in  a 
purplish  brown  discoloration  followed  by  a  disintegration  of  the 
affected  tissues  (Fig.  39).  The  accumulation  of  these  metallic  salts 
also  resulted  in  a  clogging  of  large  numbers  of  the  vascular  bundles. 
In  a  later  publication  Hoffer  and  Trost43  made  the  following  state- 
ment: 

"The  accumulation  of  iron  and  aluminum  compounds  in  the  nodal 
tissues  of  corn  plants  is  affected  by  conditions  in  the  soil  as  well  as  the 
genetical  composition  of  the  strain  of  corn.  The  accumulations  of  alum- 
inum in  the  plants  are  associated  with  retarded  growths  and  increased 
susceptibility  of  certain  strains  to  root  rots.  .  .  .  When  iron  compounds 
gradually  accumulate  in  the  nodal  tissues  of  the  plants,  the  growth  of  the 
stalks  may  be  little  affected,  but  the  disintegrations  of  the  nodal  tissues 
are  accompanied  by  increased  susceptibilities  of  the  plants  to  root  rot." 

The  reaction  of  the  soil  solution,  in  addition  to  being  an  important 
factor  in  determining  the  availability  of  phosphates  and  other  essen- 
tial plant  food  materials,  has  a  pronounced  influence  on  the  behavior 
of  parasitic  soil  fungi. 

Limestone  as  a  Corrective  for  Toxicity 

Experiments  were  begun  early  in  these  investigations  to  determine 
the  influence  of  various  applications  of  limestone  on  the  development 


320 


BULLETIN   No.   255 


[August, 


FIG.  39. — FERROUS  IRON  POISONING 
Note  the  badly  discolored  nodes. 


of  certain  of  the  corn  rot 
diseases.  Data  from  the 
University  Roland  Field, 
Urbana,  showing  the  in- 
fluence of  applications  of 
limestone  and  manure  on 
the  development  of  corn 
from  good  seed  and  from 
Diplodia-infected  seed,  are 
presented  in  Table  25.  Al- 
tho  the  corn  from  good  seed 
was  benefited  by  the  appli- 
cations in  every  case,  the 
corn  from  Diplodia-infect- 
ed seed  was  little  better  on 
the  treated  plots  than  on 
the  untreated  plots. 

Date  of  planting  ap- 
parently is  a  very  impor- 
tant factor  in  the  com- 
parative development  of 
Diplodia-infected  corn  on 
limed  and  on  unlimed  soil 
(Tables  26  and  27).  In 
the  experiment  reported  in 
Table  26,  it  will  be  noted 
that  in  the  first  planting  on 


TABLE  25. — INFLUENCE  OF  DIFFERENT  AMOUNTS  OF  LIMESTONE  ON  YIELD  FROM 
GOOD  SEED  AND  FROM  DIPLODTA-!NFECTED  SEED 

Yellow  dent  corn  grown  on  brown  silt  loam,  some  of  the  plots  receiving  no  treat- 
ment and  others  manure  and  limestone,  University  Roland  Field,  Urbana,  1922 


Character  of  seed 

Yield  on 
no-treatment 
plots 

Effect  of  different  treatments  on  acre  yield 

10  tons  manure 
4  tons  limestone 

10  tons  manure 
8  tons  limestone 

Increase       Decrease 

Increase 

Decrease 

Total  Yield 


Good  seed     ...    . 

bu. 
59  0 

bu. 
7  1 

bu. 

bu. 
9  2 

bu. 

Diplodia-infected  .... 

39.9 

0.6 

2.9 

Sound  Corn 


Good  seed  

48.5 

10.0 

11.0 

Diplodia-infected  .... 

30.1 

2.3 

3.5 

CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES 


321 


May  7  there  was  an  increase  in  both,  total  yield  and  yield  of  sound 
corn  from  Diplodia-infected  seed  for  each  of  the  three  rates  of  appli- 
cation of  lime.  In  the  plots  where  limestone  was  applied  at  the 
rate  of  12  tons  per  acre,  corn  from  Diplodia-infected  seed  yielded 
9.8  bushels  less  than  corn  from  good  seed,  altho  there  was  practically 
no  increase  in  yield  of  sound  corn  from  this  treatment.  In  the  last 
planting  there  was  a  decided  decrease  in  yield  from  Diplodia-infected 
seed  on  all  the  limed  plots. 

Similar  data  from  experimental  plots  near  Oneida  are  given  in 
Table  27  and  Chart  18.  In  the  first  planting  there  was  an  increase  of 
10.2  bushels  per  acre  in  yield  of  sound  corn  from  Diplodia-infected 
seed,  but  in  the  last  planting  there  was  a  decrease  of  13.7  bushels. 
These  data  indicate  that  both  date  of  planting  and  soil  reaction  are 
important  environing  factors  in  the  development  of  corn  from 
Diplodia-infected  seed. 

Summarized  data  of  all  the  experiments  on  the  relation  of  liming 
to  certain  of  these  diseases  are  reported  in  Table  28.  The  experiments 
were  located  on  fields  that  were  representative  of  the  large  areas  of 
brown  silt  loam  in  central  Illinois.  At  no  place  was  there  a  significant 
increase  in  yield  of  corn  from  good  seed  on  the  limed  plots.  Of  the 

TABLE  26. — INFLUENCE  OP  DIFFERENT  AMOUNTS  OF  LIMESTONE  ON  YIELD  OF  CORN  FROM 
GOOD  SEED  AND  FROM  DIPLODIA-INFECTED  SEED 

Yellow  dent  corn  grown  on  brown  silt  loam,  part  of  the  plots  receiving  no  treatment  and 
others  receiving  different  applications  of  limestone,  near  Bloomington,  1921 


Date 
of 
planting 

Character  of  seed 

Yield  on 
no-treat- 
ment 
plots 

Effect  of  different  applications  of  limestone  on  acre  yield 

4  tons 

8  tons 

12  tons 

Increase 

Decrease 

Increase  |  Decrease 

Increase    Decrease 

Total  Yield 


May    7  . 

Good  

bu. 
73.6 

bu. 

bu. 
2.3 

bu. 
2.4 

)U. 

bu. 
3  3 

6 

t. 

May  14  . 

Diplodia-infected.  . 
Good  

42.8 
69  5 

6.6 

05 

14.0 
6  5 

24.3 
8  8 

May  21  . 

Diplodia-infected.  . 
Good  

53.3 
71.2 

5.4 

9^3 

3.7 
7.6 

3.1 
13.0 

May  30  . 

Diplodia-infected.  . 
Good  

58.2 

82.7 

1.1 
3.2 

4.5 
10  0 

8.4 
3  4 

Diplodia-infected.  . 

54.4 

7.2 

9.( 

) 

4 

5 

Sound  Corn 


May    7  . 

Good  

52  3 

3  9 

0  3 

4  1 

May  14  . 

Diplodia-infected  .  . 
Good  

32.5 

47  7 

6.2 

29 

8.1 
10  8 

0.5 
15  2 

May  21  . 

Diplodia-infected.  . 
Good  

38.2 
47.5 

0.9 
0.4 

5^3 

4.6 

16  5 

2.2 

May  30  . 

Diplodia-infected.  . 
Good  

40.8 
57  6 

1.3 

76 

6.6 
5.9 

li  5 

7.3 

Diplodia-infected.  . 

35.9 

5.1 

3.8 

4.6 

BULLETIN   No.   255 


[August, 


TABLE  27. — INFLUENCE  OK  LIMESTONE  ON  YIELD  OP  CORN  FROM  GOOD 
SEED  AND  FROM  DIPLODIA-!NFECTED  SEED 

Yellow  dent  corn  grown  on  brown  silt  loam,  part  of  the  plots  receiving  no  treat- 
ment and  part  receiving  limestone,  Ontario  Parish,  near  Oneida,  1922 


Date 
of 
planting 

Character  of  seed 

Yield  on 
no-treatment 
plots 

Effect  of  4  tons  of  lime- 
stone on  acre  yield 

Increase      I     Decrease 

Total  Yield 

May    8     .  . 

Good  

bu. 
72.4 
56.1 

79.2 
61.6 

74.4 
60.7 

bu. 
4.3 
5.9 

bu. 

'8.5 

3.2 
15.7 

May  16 

Diplodia-infected  

Good 

May  29.  ... 

Diplodia-infected  

Good  

Diplodia-infected  

Sound  Corn 


May    8  

Good  

66.4 

3.5 

Diplodia-infected  

49.7 

10.2 

May  16  ... 

Good  

74.4 

1.6 

Diplodia-infected  

56.3 

9.6 

May  29 

Good  .  .        .           

69  3 

3  6 

Diplodia-infected  

52.8 

13.7 

Date  of 

Planting 

May  8        \ 
May  16        \ 
May  29       | 

Yield  of  sound  corn  on  no-treatment  plots              Effect  of  4  tons 
of  limestone  on 
uie/d 

0            70            60             50           40            JO             20            10              0              10            20 

I 

\                GooJ  Seed 

• 

Dip/odia-/nfected  Seed 

'  

1 

\                          Good  Seed 

• 

1 

Diplodia-infected  Seed              \           \ 

— 

\                   Good  Seed 

.-I  

1        DiploJia-lnfected  Seed 

I 

| 

|H  /ncmase  Decrease 

CHART  18. — DIPLODIA  INJURY  AS  INFLUENCED  BY  LIMESTONE  (Table  27) 

In  the  early  planting  liming  increased  the  yield  of  sound  corn  both 
from  good  seed  and  from  Diplodia-infected  seed.  In  the  later  plantings, 
however,  it  reduced  the  yields  except  for  an  insigniiicant  increase  in  corn 
from  good  seed. 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


TABLE  28. — SUMMARY  OF  DATA  SHOWING  THE  INFLUENCE  OF  LIMESTONE  ON  YIELD 

FROM  GOOD  SEED  AND  FROM  VARIOUS  LOTS  OF  DISEASED 

AND  DISEASE-SUSCEPTIBLE  SEED 

Corn  grown  on  brown  silt  loam  at  various  points  in  central  Illinois,  1919  to  1922 


Number  of 
years 
represented 

Number  of 
counties 
represented 

Number  of 
experiments 
represented 

Character 
of  seed 

Mean  acre  yield 

Increase 
in  yield 
on  limed 
plots 

Odds 

No 
treat- 
ment 

Limed 

4 

(1919-22) 

3 

(1920-22) 

2 
(1921-22) 

1 

(1922) 

7 
6 
6 
3 

17 
12 
6 
6 

Good  

bu. 
67.9 

57.4 
78.2 
53.9 
64.9 
57.3 

75.6 

68.4 

bu. 
70.1 

62.0 
79.1 
57.7 
66.6 
61.0 

77.1 
69.5 

bu. 
2.2 

4.6 
0.9 
3.8 
1.7 
3.7 

1.5 
1.1 

5:1 
191:1 
4:1 
6:1 
1:1 
14:1 

7:1 
3:1 

Scutellum- 
rotted 

Good  

Diplodia- 
infected.  .  . 

Good  

Fusarium- 
infected.  .  . 

Good  .  . 

Starchy  

different  diseased  composites,  corn  from  scutellum-rotted  seed  was 
the  only  one  to  show  a  significant  increase  in  yield  for  the  limed  plots, 
the  increase  being  4.6  bushels  per  acre,  with  odds  of  191  to  1,  as  con- 
trasted with  an  increase  of  2.2  bushels,  with  odds  of  5  to  1,  in  the  corn 
from  good  seed. 


INFLUENCE    OF    CROP   SEQUENCE 

Previous  cropping,  or  crop  sequence,  is  one  of  the  most  important 
environing  factors  determining  the  extent  of  injury  caused  by  corn 
rot  diseases.  In  the  experiments  reported  in  Table  29  the  com- 
parisons were  made  in  the  same  or  closely  adjacent  fields  of  the  same 
soil  type  and  as  nearly  alike  in  all  other  factors  as  possible.  In  no 
case  was  there  a  difference  of  more  than  one  day  in  date  of  planting. 
Where  corn  followed  corn  or  wheat  the  reduction  in  acre  yield 
from  scutellum-rotted  seed  was  significantly  greater  in  every  instance 
than  where  corn  followed  a  legume,  prairie  sod,  or  oats.  In  the  ex- 
periment at  Bloomington  in  1920  there  was  a  difference  of  14.1  bushels 
in  acre  yield  between  corn  from  good  seed  and  from  scutellum-rotted 
seed  where  corn  followed  clover,  but  in  the  same  field  where  corn  fol- 
lowed badly  scabbed  spring  wheat  the  difference  was  33.1  bushels. 
Results  in  1921  were  very  similar.  There  was  a  reduction  of  11.8 
bushels  in  acre  yield  of  sound  corn  on  the  virgin  soil  field,  but  a  re- 
duction of  31.3  bushels  just  across  the  fence  on  soil  that  had  been  in 
grain  crops  the  preceding  years.  At  Peoria,  in  1921,  the  difference  in 
the  yield  of  corn  from  good  seed  and  from  scutellum-rotted  seed  was 


324 


BULLETIN   No.   255 


[August, 


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CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES 


325 


FIG.  40. — INFLUENCE  OF  CROP  ROTATION  ON  INJURY  FROM  SCUTELLUM  ROT 

Rows  on  the  left  are  from  scutellum-rotted  seed;  those  on  the  right 
are  from  good  seed.  Above,  first  year  corn  after  a  legume  in  a  rotation 
of  soybeans,  corn,  corn,  corn.  Below,  first  year  corn  after  a  legume  in  a 
rotation  of  clover,  corn,  corn,  wheat.  Soil  treatments  have  been  the  same 
in  each  rotation  and  the  date  of  planting  was  the  same.  University  South 
Farm,  Urbana. 

Corn  from  good  seed  responded  better  to  more  favorable  conditions  in 
crop  rotations  than  did  corn  from  scutellum-rotted  seed.  Data  from  these 
rotations  up  to  the  present  time  indicate  that  crop  rotation  is  as  important 
a  factor  in  determining  yield  of  corn  as  are  soil  treatments. 


326 


BULLETIN   No.    255 


[August, 


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CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES 


327 


5.1  bushels  per  acre  where  corn  followed  clover  and  12.7  bushels  where 
corn  followed  corn.  Results  at  Cambridge  the  following  year  were 
similar. 


TIG.  41. — INFLUENCE  OF  CROP  SEQUENCE  ON  INJURY  FROM  SCUTELLUM  ROT 

The  reduction  in  yield  of  sound  corn  from  scutellum-rotted  seed  (right) 
as  compared  with  the  yield  from  good  seed  (left)  was  very  much  greater 
in  the  field  where  corn  followed  soybeans  in  a  rotation  of  corn,  corn,  corn, 
soybeans  (below)  than  where  it  was  the  third  year  of  corn  in  the  same 
rotation  (above)  (Table  30).  Of  the  environing  factors  affecting  the 
development  of  the  different  corn  rot  diseases,  the  problem  of  crop  rota- 
tion and  crop  sequence  takes  a  place  second  to  no  other  under  conditions 
existing  at  the  present  time  in  central  Illinois. 


328  BULLETIN   No.   255  [August, 

Since  1920,  plantings  of  good  seed  and  various  lots  of  diseased  seed 
have  been  made  in  three  long-time  rotations  on  the  University  South 
Farm,  Urbana.  A  summary  of  three  years'  field  data  from  good  seed 
and  from  scutellum-rotted  seed  is  presented  in  Table  30.  In  the 
Northwest  rotation  the  acre  yields  of  sound  corn  averaged  63.6  bushels 
and  49.9  bushels,  respectively,  showing  a  reduction  of  13.7  bushels  due 
to  scutellum-rotted  seed.  Soil  treatments  on  the  North-Central  and 
the  South-Central  rotations  have  been  the  same  since  the  rotations 
were  started  in  1907.  They  have  consisted  of  an  application  of  rock 
phosphate  at  the  rate  of  2,000  pounds  per  acre  every  four  years. 

Data  from  these  rotations  up  to  the  present  time  indicate  that  crop 
rotation  is  as  important  a  factor  in  determining  yield  of  corn  as  are 
soil  treatments  (Fig.  40).  'Corn  from  good  seed  responded  better 
to  the  more  favorable  conditions  in  each  rotation  than  did  corn  from 
scutellum-rotted  seed.  Of  the  environing  factors  affecting  the  de- 
velopment of  the  different  corn  rot  diseases  under  discussion  in  this 
bulletin,  the  problem  of  crop  rotations  (Fig.  40)  and  crop  sequence 
(Fig.  41)  takes  a  place  second  to.  no  other  under  conditions  existing 
at  the  present  time  in  central  Illinois. 

GENETIC  FACTORS 

From  the  data  and  discussion  presented  up  to  this  point  it  is  evi- 
dent (1)  that  pathogenic  bacteria  and  fungi  are  capable  of  causing 
diseases  of  great  economic  importance  to  the  corn  crop  under  condi- 
tions usually  existing  in  the  corn  belt,  and  (2)  that  such  environing 
factors  as  soil  temperature,  soil  moisture,  soil  aeration,  available  plant 
food  materials,  soil  toxicity,  and  crop  sequence  exercise  a  strong  influ- 
ence on  the  development  and  expression  of  disease. 

However,  the  extent  to  which  the  corn  plant  is  affected  by  either 
parasitic  or  environing  factors  depends  largely  on  the  inherent 
qualities,  or  genetic  composition,  of  the  particular  corn  plant  in 
question.  Certain  strains  of  corn,  on  account  of  their  superior  in- 
herent qualities,  are  able  to  develop  and  function  normally  under 
a  wide  range  of  environmental  conditions,  while  other  strains  vary 
greatly  in  their  susceptibility  to  injury  when  grown  in  association 
with  the  same  environmental  and  parasitic  factors.  Differences  in 
genetic  factors  seem  to  be  the  only  logical  explanation  for  these 
variations. 

A  large  number  of  genetic  characters,  including  abnormalities, 
chlorophyll  deficiencies,  and  seed  characters,  have  received  much 
attention  by  a  number  of  investigators,  a  summary  of  whose  work 
has  been  given  by  Lindstrom62  and  by  Wallace  and  Bressman.112 
In  addition  to  the  work  on  individual  genetic  factors,  certain  linkage 
groups  have  been  established.  The  relation  of  all  these  known  fac- 


1984] 


CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES 


329 


tors  to  disease  resistance  and  productiveness  of  seed  corn  has  not 
been  determined,  but  it  is  common  observation  that  corn  containing 
many  weak  and  undesirable  characters  is  not  likely  to  yield  satis- 
factorily. In  addition  to  the  heritable  characters  already  known  there 
undoubtedly  are  many  other  characters  which  are  very  important  in 

determining     the     be- 

havior  of  a  strain  of 
corn  and  its  ability  to 
resist  disease  and  in- 
jury from  unfavorable 
environments.  Hoffer 
and  Carr42  suggested 
that  selective  absorp- 
tion by  individual  corn 
plants  may  prove  to  be 
a  very  important  herit- 
able character.  Hoffer 
and  Trost43  later  pub- 
lished data  which  gave 
support  to  this  sugges- 
tion. Holbert  and 
Koehler49  showed  that 
inbred  strains  differ 
greatly  in  the  charac- 
ter and  extent  of  their 
root  systems.  Certain 
strains,  apparently  in- 
dependent of  any  para- 
sitic factors,  have  such 
a  limited  and  inefficient 
root  system  (Fig.  42) 
that  they  are  unable  to 
function  normally  dur- 
ing the  hot  days  of 
July  and  August,  when 
the  soil  moisture  is 
low  (Fig.  43). 

Other  strains  not 
only  have  fewer  roots 
and  a  lower  ratio  of 
tops  to  roots,  but  are 
very  susceptible  to  a 
rotting  of  the  roots  and  to  injury  from  inoculation  with  Gibberella 
saubinetii  (Fig.  44).  Data  illustrating  this  behaviour  are  given  in 
Tables  31  and  32.  In  the  two  unrelated  strains  reported  in  Table  31, 


FIG.   42. — HERITABLE  DIFFERENCES  IN  EXTENT  AND 
CHARACTER  OF  BOOT  SYSTEMS 

Representative  root  systems  of  two  inbred  strains 
of  dent  corn.  The  one  illustrated  above  is  susceptible 
to  leaf  firing;  the  lower  one  is  highly  resistant  to 
both  leaf  firing  and  root  rot.  Note  difference  in 
character  and  extent  of  the  two  root  systems. 


330 


BULLETIN   No.    255 


[August, 


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CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


331 


differences  in  height,  circumference  at  base  of  plant,  total  number  of 
roots,  and  air-dry  weights  of  tops  and  roots  were  all  significant.  The 
ratio  of  tops  to  roots  in  the  good  strain  (A-1-1-2-R-3-2)  was  1  to  0.83, 
while  in  the  weak-rooted  strain  (B-1-1-1-R-8-2)  it  was  1  to  0.66 
(Fig.  45).  This  difference  in  the  two  ratios  was  fairly  consistent  for 
the  plants  studied,  the  odds  being  87  to  1.  Uninoculated  plants  pro- 


FIG.  43. — SUSCEPTIBILITY  (Left)  AND  RESISTANCE  (Right)  TO  INJURY 
FROM  DROUTH 

Certain  strains,  apparently  independent  of  any  parasitic  fac- 
tors, have  such  a  limited  and  inefficient  root  system  that  they  are 
unable  to  function  normally  during  the  hot  days  of  July  and 
August  under  conditions  of  low  soil  moisture. 

duced  a  mean  plant  yield  of  0.575  and  0.428  pound,  respectively,  while 
inoculated  plants  yielded  0.549  and  0.328  pound,  respectively.  Thus 
the  yield  of  the  good  strain  was  reduced  only  0.026  pound  per  plant 
by  the  inoculation,  while  the  yield  of  the  weak-rooted  strain  was  re- 
duced 0.10  pound  per  plant. 

The  two  strains  reported  in  Table  32  were  very  closely  related. 
In  1922  they  differed  greatly  in  pulling  resistance,  the  resistance  of 


332 


BULLETIN   No.   255 


[August, 


FIG.  44. — HERITABLE  DIFFERENCES  IN   ROOT   SYSTEMS 
Representative  root  systems  of  two  inbred  strains  of  dent  corn, 
one  of  which  (above)  is  susceptible  to  root  rot  and  the  other  (below) 
highly  resistant.     Note  the  difference  in  extent  and  branching  of  the 
lateral  roots. 


W24] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


333 


FIG.  45. — DIFFERENCE  IN  RATIO  OF  TOPS  TO  ROOTS 
Representative  plants  of  the  two  unrelated 
inbred  strains.  At  the  left,  strain  A-1-1-2-R-3-2; 
at  the  right  strain  B-1-1-1-R-8-2  (Table  31).  Note 
difference  in  number  of  roots  as  well  as  in  mass. 


334 


BULLETIN   No.   255 


[August, 


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CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


335 


one  being  364  pounds  and  that  of  the  other  120  pounds.  In  1923 
the  mean  resistance  was  280.6  pounds  for  the  one  and  147.6  pounds 
for  the  other  (Fig.  46).  The  weaker  rooted  strain  (B-l-1-1-1-8)  not 
only  yielded  less  in  the  uiiinoculated  plots,  but  was  much  more  sus- 
ceptible to  injury  from  inoculation,  the  reduction  in  yield  being  15.5 
bushels  per  acre  with  odds  of  71  to  1,  as  compared  with  a  reduction 
in  the  strong-rooted  strain  (B-l-1-1-1-7)  of  only  2.1  bushels  with 
odds  of  3  to  1. 


FIG.  46. — HERITABLE  DIFFERENCES  IN  ANCHORAGE  OF  CORN  PLANTS 

A  weak-rooted  inbred  strain   growing  between   corn   from  a 
strong-rooted  inbred  strain  which  was  closely  related   (Table  32). 

On  the  other  hand,  strains  of  corn  with  the  same  total  number 
of  main  roots  may  differ  greatly  in  their  resistance  to  root  rot  (Figs. 
47  and  48).  In  the  more  strongly  rooted  strain  (G-4-2-1)  reported 


336 


BULLETIN    No.   255 


[August, 


in  Table  33,  only  1.5  percent  of  the  main  roots  were  rotted  on  July  21, 
while  in  the  strain  susceptible  to  leaf  firing  and  root  rot  (G-4-4-1), 
24.0  percent  of  the  main  roots  were  rotted.  The  difference  of  0.8 
in  number  of  main  roots  was  not  significant.  However,  there  were 
marked  differences  in  number  of  fibrous  roots  (Fig.  49).  The  ratio 


FIG.  47. — SUSCEPTIBILITY  AND  RESISTANCE  TO  BOOT  ROT 
Portions  of   two   root  systems,   the   one   on   the   left   being  very   sus- 
ceptible to  root  rot  and  the  other  highly  resistant. 

of  tops  to  roots  in  the  good  strain  was  1  to  0.85,  while  in  the  susceptible 
strain  this  ratio  was  1  to  0.62.  During  the  latter  part  of  the  growing 
season  there  was  much  firing  of  the  lower  leaves  in  the  susceptible 
strain,  and  by  the  middle  of  September  practically  all  the  roots  were 
rotted.  This  difference  in  the  two  strains  in  resistance  and  suscepti- 
bility to  root  rot  was  reflected  in  the  yield  of  grain.  The  good  strain 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


337 


yielded  0.607  pound  per  plant,  while  the  susceptible  strain  yielded 
only  0.251  pound. 

In  general  it  has  been  found  that  weak-rooted  strains,  when 
compared  with  better  rooted  strains,  are  more  likely  to  lodge  and  are 
lower  in  grain  production  (Fig.  50),  owing  in  part  to  being  more  sus- 
ceptible to  injury  from  unfavorable  environment  and  in  part  to 
parasitic  factors,  as  is  shown  by  data  presented  in  Table  34.  The 
final  field  stands  of  strong-rooted  and  weak-rooted  strains  in  the 
uninoculated  plots  were  practically  the  same,  90.2  and  90.0  percent, 
respectively.  The  mean  yield  of  the  strong-rooted  strains  was  64.5 
bushels  per  acre,  while  that  of  the  weak-rooted  was  38.8  bushels. 


Acre  y/e/d  of  sound  corn  from  uninocu/ated  seed 
(Previous  crop  sequence  -char,  of  strain) 

100      90      80       70       60       50      40      30       20       10 


Decrease  in  yield 
following  inoco/ation 


to      20 


May  // 


May  10 


{Vfrgin  prairie  sod  -  Good) 


^Virgin  prairie  sod- D.-Susce$\ 


{(Corn  oats,  wheat  -  Good} 


\Corn,  oats,  wheat- D.-suscep) 


Date,  of 
planting 

May  II 
May  10 


Mean  percent  field  stand  from 
uninoculated  seed 

(Previous  crop  sequence -char,  of  strain) 

/OO         90       8O         70         60        50         40         30        20         10 


(Virgin  prairie  sod  -   Good) 


Decrease  in 
field  stand 
following 
inoculation 

)          10        20 


\(Virgin  prairie  sod  -  D/sease-susceptib/e) 


(Corn  oats,  wheat  -  Good)                         • 

.  oats,  wheat-  Disease-susceptible 


CHART  19. — DISEASE  RESISTANCE  IN  OPEN-POLLINATED  STRAINS 
(Table  35) 

The  yields  from  the  open-pollinated  strain  selected  for  disease  re- 
sistance and  planted  in  clean  soil  and  in  infested  soil  were  only  slightly 
reduced  by  inoculation  with  G.  saubinetii.  The  yields  from  a  susceptible 
strain  under  like  conditions  were  significantly  reduced  on  both  clean  and 
infested  soil.  Also,  the  only  significant  reduction  in  field  stand  following 
inoculation  occurred  where  seed  of  susceptible  strains  was  used. 


333 


BULLETIN   No.   255 


[August, 


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CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES 


339 


Inoculation  with  Gibberella  saubinetii  reduced  the  mean  yield  of  the 
strong-rooted  strains  4.7  bushels  per  acre,  while  it  reduced  the  mean 
yield  of  the  weak-rooted  strains  10.4  bushels.  In  the  former  case 
the  odds  were  81  to  1 ;  in  the  latter  they  were  more  than  9999  to  1. 
Altho  variations  in  disease  resistance  are  greater  in  open-pollinated 
corn  than  in  uniform  inbred  strains,  yet  there  are  open-pollinated 
strains  that  are  highly  resistant  to  certain  of  the  corn  rot  diseases. 
This  resistance  can  be  maintained  by  constant  selection.  Table  35 
and  Chart  19  present  data  from  an  inoculation  experiment  in  which 


FIG.  48. — HEALTHY  AND  ROTTED  ROOTS 

Representative  roots  from  a  strain  highly  resistant  to  root  rot   (left) 
and  from  a  strain  susceptible  to  root  rot  (right). 

disease-suceptible  open-pollinated  strains  were  compared  with  an  open- 
pollinated  strain  that  had  been  selected  for  disease  resistance  for  a 
number  of  years.  The  field  plantings  were  made  under  conditions 
which  Dickson  has  shown  to  be  favorable  for  injury  from  G.  saubinetii. 
Inoculation  with  this  organism  in  plantings  following  virgin  prairie 
sod,  reduced  the  mean  total  yield  of  corn  from  susceptible  strains  14.8 
bushels  per  acre,  with  odds  of  713  to  1,  while  under  the  same  condi- 
tions it  reduced  the  total  yield  of  the  corn  from  the  good  seed  only 


340 


BU.LLETIN   No.   255 


FIG.   49. — HERITABLE   DIFFERENCES  IN   CHAR- 
ACTER OF  EOOT  SYSTEMS   (Table  33) 

Representative  plants  of  two  inbred  strains. 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


341 


1.8  bushels  per  acre,  with  odds  of  5  to  1.  With  the  good  strain 
in  this  experiment  there  was  practically  no  reduction  in  the  yield  of 
sound  corn  following  inoculation,  but  with  the  disease-susceptible 
strains  there  was  a  reduction  of  12.5  bushels  per  acre,  with  odds  of 
1249  to  1. 

Results  from,  the  plantings  following  wheat  were  in  accord  with 
the  foregoing  results  from  the  planting  following  virgin  sod,  tho  the 
reductions  in  the  disease-susceptible  plots  were  not  so  pronounced. 

Complete  resistance  or  immunity  to  a  majority  of  the  corn  rot 
diseases  seems  possible  only  by  the  recombination  of  two  or  more 
highly  resistant  and  reasonably  productive  inbred  strains  which  nick 


FIG.   50. — HERITABLE   DIFFERENCES  IN  ANCHORAGE  OF  CORN   PLANTS 

Certain  inbred  strains  of  corn  are  weakly  anchored  and  conse- 
quently blow  down  easily.  Other  strains  are  well  anchored  and  are 
able  to  withstand  all  ordinary  wind  and  rain  storms.  The  performance 
of  such  strains  has  been  found  to  be  consistent  over  a  period  of  years 
as  reported  by  Koehler,  Dungan,  and  Holbert.  Bloomington. 


342 


BULLETIN   No.   255 


[August, 


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CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


343 


together  in  a  compatible  way,  an  illustration  of  which  is  given  in 
Table  36  and  Figs.  51,  52,  and  53.  These  data,  as  well  as  those 
reported  in  Tables  31  to  35  inclusive,  indicate  that  genetic  factors  are 
as  important  as  environmental  factors  (Table  4)  in  determining  re- 
sistance to  Gibberella  root  rot  and  seedling  blight  disease. 

In  comparing  good  open-pollinated  corn  with  this  first-generation 
cross  reported  in  Table  36,  it  will  be  noted  that  the  percentage  of 
inclined  plants  was  reduced  from  12.8  percent  to  0.1  percent  in  the 
cross,  and  the  percentage  of  smutted  plants  from  2.5  to  0.1  percent. 


FIG.  51. — A  GOOD  FIRST  GENERATION  CROSS    (LEFT)    AND  A  POOR 
ONE   (RIGHT) 

First-generation  crosses  between  inbred  strains  vary  greatly  in 
their  ability  to  stand  erect  during  strong  wind  storms.  Many  crosses 
are  very  inferior  to  the  original  variety,  while  a  few  are  decidedly 
superior  in  every  respect.  The  cross  on  the  left  is  illustrated  also  in 
Figs.  52  and  53  (Table  36). 


344 


BULLETIN   No.   255 


[August, 


The  total  yield  was  increased  from  90.5  ±  1.0  bushels  per  acre  in  the 
open-pollinated  corn  to  117.2  ±  1.6  bushels  in  the  first-generation 
cross.  The  yield  of  sound  corn  was  increased  from  85.9  ±  0.5  bushels 
per  acre  to  110.5  ±  2.9  bushels.  This  same  cross  gave  similar  results 


FIG.  52. — Two  METHODS  OF  CORN  BBEEDING 

Above,  corn  from  good  open-pollinated  seed ;  below,  corn  from  the 
first-generation  cross  of  two  compatible  and  highly  resistant  inbred  strains 
of  the  same  variety  as  above  (Table  36  and  Fig.  53).  Farm  of  Mr.  E.  D. 
Funk,  near  Bloomington,  1923. 


CORN  SOOT,  STALK,  AND  EAII  ROT  DISEASES 


345 


the  previous  three  years.  Further  data  and  discussion  of  disease  re- 
sistance and  its  relation  to  corn  improvement  will  be  found  in  other 
sections  of  this  bulletin. 


FIG.  53. — EACH  METHOD  OF  BREEDING  HAS  ITS  PLACE  IN  A  PROGRAM 
OF  CORN  IMPROVEMENT 

Same  plots  as  shown  in  Fig.  52,  but  with  leaves  stripped  to  show 
uniformity  in  good  characteristics.  Complete  resistance  or  immunity 
to  a  majority  of  the  corn  rot  diseases  seems  possible  only  by  the 
recombination  of  two  or  more  highly  resistant  and  reasonably  productive 
inbred  strains  which  nick  together  in  a  compatible  way. 


346  BULLETIN   No.   255  [August, 

PART  III 
ECONOMIC  IMPORTANCE  OF  CORN  ROT  DISEASES 

It  is  difficult  to  estimate  accurately  the  losses  to  corn  growers 
resulting  from  the  use  of  infected  seed  and  seed  of  corn  especially 
susceptible  to  disease  and  to  injuries  under  unfavorable  soil  and 
weather  conditions.  Severity  of  the  losses  depends  on  many  factors, 
chief  among  which  are  soil  management  and  soil  fertility,  crop 
sequences  and  crop  rotation  systems,  climatic  and  seasonal  conditions, 
time  of  planting,  and  quality  of  strain  and  of  seed.  The  use  of  such 
seed  undoubtedly  is  responsible  for  losses  to  the  extent  of  25  to  50 
percent  on  many  farms  in  the  corn  belt.  Occasionally,  especially  with 
sweet  corn,  these  diseases  have  resulted  in  the  loss  of  almost  an  entire 
crop.  Losses  frequently  vary  from  less  than  5  percent  to  as  much 
as  50  percent  on  adjoining  farms,  depending  on.  the  character  and 
condition  of  seed  used  and  the  kind  of  farming  practiced.  Parts  of 
fields  have  commonly  been  found  in  which  the  grain  was  damaged 
to  the  extent  of  25  percent  by  ear  rots  alone,  while  in  other  parts  of 
the  same  fields  grain  from  good  seed  was  damaged  but  little. 

FIELD  EXPERIMENTS  WITH  VARIOUS  SEED  SELECTIONS 

Since  1917  experiments  have  been  conducted  to  determine,  as 
nearly  as  possible,  the  loss  due  to  corn  rot  diseases  thru  the  use  of 
seed  the  progeny  from  which  was  susceptible  to  disease. 

SCUTELLUM-ROTTED  SEED 

The  data  from  the  experiments  with  scutellum-rotted  seed  are  sum- 
marized in  Table  37.  The  scutellum-rotted  seed  used  in  these  experi- 
ments was  probably  as  good  as  most  of  the  seed  planted  thruout  the 
state  during  those  years.  All  lots  of  nearly  disease-free  seed  used  were 
good  in  vitality  and  comparatively  free  from  infection  with  organisms 
known  to  be  parasitic  to  corn.  The  difference  in  the  yields  from  the 
scutellum-rotted  seed  and  from  the  good  seed,  ranging  from  less 
than  3  percent  to  approximately  50  percent  (Table  37  and  Chart  20), 
suggests  that  scutellum-rotted  seed  is  a  probable  cause  of  reduction 
in  yield.  On  the  basis  of  sound  corn,  reductions  in  yield  were  much 
greater  than  the  above. 

Under  the  most  favorable  conditions  scutellum-rotted  seed  usually 
produces  a  satisfactory  field  stand.  However,  if  the  weather  and  soil 
conditions  are  very  unfavorable  for  germination  of  corn,  the  use  of 
such  seed  may  result  in  a  failure.  Different  lots  of  scutellum-rotted 


1924]  CORN  KOOT,  STALK,  AND  EAR  ROT  DISEASES  347 

seed  vary  greatly  in  their  ability  to  germinate  and  yield  well  under 
adverse  conditions.  While  occasionally  certain  lots  are  only  slightly 
inferior  to  good  seed,  in  general  it  may  be  said  that  they  are  distinctly 
inferior  and  in  certain  instances  are  no  better  than  Diplodia-infected 
seed  under  the  same  adverse  conditions. 

DIPLODIA-INFECTED  SEED 

Of  the  parasitic  organisms  causing  ear  rots  and  seed  infections, 
Diplodia  zeae  is  one  of  the  most  important.  Every  year  there  is  an 
appreciable  amount  of  the  corn  crop  damaged  by  ear  rots  for  which 
Diplodia  is  chiefly  responsible.  However,  damage  from  Diplodia  is 
not  confined  to  badly  rotted  ears.  The  organism  may  be  present  in 
many  apparently  good  ears  that  are  selected  for  seed  purposes.  In 
some  lots  of  seed  corn  prepared  by  farmers,  50  percent  of  the  kernels 
have  been  found  to  be  infected  chiefly  with  Diplodia  zeae,  while  in 
other  lots  of  seed,  similarly  prepared,  only  a  few  kernels  were  found 
to  be  infected  with  this  organism.  Planting  of  Diplodia-infected  seed 
always  lias  resulted  in  a  reduced  stand,  many  blighted  and  weak 
plants,  and  a  lowered  vigor  and  vitality  of  those  plants  which  survive. 

Table  38  and  Chart  21  present  yield  data  for  four  years  from 
experiments  the  object  of  which  was  to  compare  the  behavior  of  corn 
grown  from  Diplodia-infected  seed  with  that  grown  from  good  seed. 
Reductions  in  yield  following  the  planting  of  seed  infected  with  this 
organism  varied  from  less  than  15  percent  to  more  than  50  percent, 
depending  on  date  of  planting,  soil  temperature,  and  soil  moisture, 
especially  during  the  first  two  weeks  following  planting,  previous 
cropping,  and  the  fertility  of  the  soil. 

Durrell,22  of  the  Iowa  Agricultural  Experiment  Station,  makes 
the  following  significant  statements  regarding  the  economic  importance 
of  this  disease : 

' '  The  study  of  the  dry  rot  disease  of  corn  caused  by  Diplodia  zeae  shows 
it  to  be  a  prevalent  disease  in  Iowa,  resulting  in  losses,  the  past  two  seasons, 
ranging  from  3  to  15  percent  of  the  ears  at  harvest  and  a  11  percent 
damage  to  the  seed  corn.  The  loss  in  stand  from  diseased  seed  in  many 
fields  amounted  to  15  percent.  A  still  further  loss  results  from  nodal 
infection  and  weak  plants  grown  from  slightly  infected  seed." 

FUSARIUM-INFECTED  SEED 

Seed  infection  with  Fusarium  moniliforme  is  of  considerable  eco- 
nomic importance.  Altho  extensive  field  inoculation  studies  have 
failed  to  yield  definite  data  concerning  the  pathogenicity  of  this 
organism,  the  planting  of  seed  primarily  infected  with  Fusarium 
moniliforme  has  consistently  resulted  in  a  reduced  yield  of  sound 
corn.  Where  conditions  are  favorable  thruout  the  growing  season, 
the  reductions  may  be  only  very  slight,  but  under  certain  soil  condi- 


348 


BULLETIN   No.   255 


[August, 


TABLE  37. — YIELDS  OP  CORN  FROM  GOOD  SEED  AND  FROM  SCUTELLUM-ROTTED  SEED 
Grown  at  various  points  in  Illinois,  1917  to  1923 


Year 

Location  of 
experiment 
(Illinois) 

Previous  crop 

Relative  time 
of  planting 

Acre  yield 

Reduction 
following  use  of 
scutellum-  rotted 
seed 

Good 
seed 

Scutel- 
lum-rot- 
ted  seed 

1917 

Bloomington.  .  .  . 
Bloomington.  .  .  . 

Sweet  clover  
Corn  

Early  
Early  

bu. 
90.0 
102.5 

bu. 
79.0 
67.5 

bu. 
11.0 
35.0 

perct. 
12.2 
34.1 

1918 

Bloomington.  .  .  . 
Bloomington.  .  .  . 

Side'.l  

Corn  
Winter  wheat  

Corn  

Early  
Early  .  

Intermediate.  .  . 

70.1 
67.0 

77.4 

49.6 
54.0 

62.7 

20.5 
13  0 

14.7 

29.2 
19.4 

19.0 

1919 

Bloomington.  .  .  . 
Bloominaton.  .  .  . 
Bloomington.    .  . 

Clover  
Alfalfa  

Early  
Early  

71.2 
82.0 
81.3 
90.9 

72.2 

55.2 
69.5 
60.0 
80.7 

66.9 

16.0 
12.5 
21.3 
10.2 

5.3 

22.5 
15.2 
26.2 
11.2 

7.3 

Spring  wheat  
Clover  

Intermediate.  .  . 
Intermediate.  .  . 

Yates  City 

Clover  

Intermediate.  .  . 

1920 

Urbana  

Potatoes  
Clover  

Clover  

Intermediate.  .  . 
Intermediate.  .  . 

Intermediate.  .  . 

77.8 
86.7    '. 

89.0 
44.4 
59.0 
69.7 
67.1 
70.3 
57.3 

,    63.5 
69.8 

86.7 
36.3 
50.9 
60.8 
51.1 
58.3 
48.6 

14.3 
16.9 

2.3 

8.1 
8.1 
8.9 
16.0 
12.0 
8.7 

18.4 
19.5 

2.6 
18.2 
13.7 
12.8 
23.8 
17.1 
15.2 

Urbana  

Corn  

Intermediate.  .  . 

Decatur  

Corn  

Intermediate.  .  . 

Yates  City 

Corn  

Intermediate.  . 

Virginia  
Morris  

Clover  
Clover  
Corn  

Late  
Intermediate.  .  . 
Intermediate.  .  . 

1921 

Peoria  

Corn  

Early  

81.5 

91.0 

86.6 
93.8 

103.5 
101.9 
94.3 
92.3 

86.2 
96.8 

74.9 

74.7 
70.3 

68.7 
65.8 

66.6 

88.3 
75.8 
84.5 

94.0 

88.0 
84.9 
80.5 

81.7 
82.8 

70.9 
68.3 
68.7 

63.0 
56.4 

14.9 

2.7 
10.8 
9.3 

9.5 
13.9 
9.4 
11.8 

4.5 
14.0 

4.0 
6.4 
1.6 

5.7 
9.4 

18.3 

3.0 
12.5 
9.9 

9.2 
13.6 
10.0 
12.8 

5.2 
14.5 

5.3 
8.6 
2.3 

8.3 
14.3 

Bloomington.  .  .  . 
Bloomington.  .  .  . 

Virgin  prairie  
Corn  

Early  
Early  

Bloomington.  .  .  . 
Urbana  

Virgin  prairie  

Potatoes  
Potatoes  

Late  

Early  
Intermediate.  .  . 

Urbana 

Potatoes  

Intermediate.  .  . 

Potatoes  .  .  . 

Late  

Amboy  
Amboy  

Intermediate.  . 
Intermediate.  .  . 

Ontario  Parish  .  . 
Ontario  Parish  .  . 
Ontario  Parish  .  . 

Cambridge  
Cambridge  

Timothy  
Timothy  
Timothy  

Oats  
Corn  

Early  
Intermediate.  .  . 
Late  

Intermediate.  .  . 
Intermediate.  .  . 

1922 

Bloomington.  .  .  . 

Urbana  
Urbana  

Corn,  2d  year  on 
virgin  sod  

Clover  
Corn  
Potatoes  

Intermediate.  . 

Intermediate.  .  . 
Intermediate.  .  . 
Early    

100.2 

59.9 
33.3 
59.2 
58.3 
56.1 
53.0 

94.3 

51.2 

28.2 
57.5 
54.6 
44.7 
41.0 

5.9 

8.7 
5.1 
1.7 
3.7 
11.4 
12.0 

5.9 

14.5 
15.3 
2.9 
6.3 
20.3 
22.6 

Urbana      

Potatoes  

Intermediate.  .  . 

Urbana  

Potatoes  

Late  

CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES 


34!) 


TABLE  37. — Concluded 


Year 

Location  of 
experiment 
(Illinois) 

Previous  crop 

Relative  time 
of  planting 

Acre  yield 

Reduction 
following  use  of 
scutellum-rotted 
seed 

Good 
seed 

Scutel- 
lum-rot- 
ted  seed 

1923 

Bloomington.  .  .  . 
Bloomington  .... 

Alfalfa          .    . 

Early    

bu. 
85.0 
90.4 

62.9 
61.7 
63.3 
62.9 
63.1 
55.1 

67.4 

78.7 

65.7 
70.0 
59.2 

bu. 
65.0 
70.9 

47.8 
48.3 
54.7 
56.4 
41.7 
38.4 

54.8 
47.1 

33.0 
55.2 
36.8 

bu. 
20.0 
19.5 

15.1 
13.4 
8.6 
6.5 
21.4 
16.7 

12.6 
31.6 

32.7 

14.8 
22.4 

perct. 
23.5 
21.6 

24.0 
21.7 
13.6 
10.3 
33.9 
30.3 

18.7 
40.2 

49.8 
21.1 
37.8 

Alfalfa  

Late  

Prairie  sod  

Early  

Cambridge  

Prairie  sod  

Late  

Early 

Cambridge  

Prairie  sod  

Late  

Cambridge  

Corn  

Early  
Late   

Intermediate.  .  . 
Late  

Hopedale  

Corn  

Urbana  

Clover    

Early  

Urbana  
Urbana  

Clover  
Clover  

Intermediate.  .  . 
Late  

Mean  reduction  in  acre  yield  of  sound  corn  in  plots  planted  with  scutellum-rotted 
seed,  12.4  +  0.66  bushels. 

12.4 
=  18.8.     Odds  greater  than  one  million  to  one. 

0.1)6 


/oo 

90 

60 

a 

c  70 


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iiiiiiiiiiiii 


20 


/O 


Hill! 


> 
,§ 


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CHART  20. — COMPARATIVE  YIELDS  FROM  GOOD   SEKD  AND  FROM   SCUTELLUM- 
EOTTED  SEED   (Table  37) 


350 


BULLETIN   No.   255 


tions  Fusarium-infected  seed  has  yielded  little  more  than  Diplodia- 
infected  seed. 

Data  for  three  years  from  experiments  comparing  corn  grown 
from  good  seed  with  corn  grown  from  seed  infected  with  Fusarium 
spp.  are  summarized  in  Table  39.  The  reductions  in  yield,  ranging 


TABLE  38.- 


-  YIELDS  OF  DENT  CORN  FROM  GOOD  SEED  AND  FROM 

DlPLODIA-lNFECTED  SEED 


Year 

Location  of 
experiment 
(Illinois) 

Previous  crop 

Relative 
time  of 
planting 

Acre  yield 

Reduction  in 
sound  corn  fol- 
lowing use  of 
infected  seed 

Good  seed 

Seed  infected 
with 
Diplodia  zeae 

Total 

Sound 

Total 

Sound 

1920 

Urbana  

Alfalfa   

Early  

bu. 
103.9 

73.6 
69.5 
71.2 
82.7 

59.8 
55.6 

bu. 

52.3 

47.7 
47.5 
57.6 

52.1 

48.2 

bu. 

60.7 

42.8 
53.3 

58.2 

>,  54.4 

49.0 
46.9 

bu. 

32.5 
38.2 
40.8 
35.9 

39.9 
40.1 

bu. 

19.8 
9.5 
6.7 
21.7 

12.2 
8.1 

perct. 

37.9 
19.9 
14.1 
37.7 

23.4 
16.8 

Bloomington  .  . 

Corn  
Corn 

Early  ....... 
Intermediate 
Intermediate 
Late  

Intermediate 
Intermediate 

Bloomington    . 

Corn  

Bloomington.  . 
Clinton  

Corn  
Corn  

Clover 

1921 
1922 

Peoria  
Virginia    .    .  . 

Clover  
Clover      

Intermediate 
Late. 

75.8 
65.9 

100.0 
71.8 

59.6 
35.0 
59.2 
58.3 
56.1 
53.0 

59.4 

58.7 

93.7 
61.1 

49.3 
27.6 
45.0 
44.8 
46.6 
45.5 

58.6 
54.2 

78.9 
47.9 

29.4 
19.3 
41.0 
32.1 
33.6 
29.2 

46.5 
42.6 

72.1 
39.0 

25.4 
12.8 
31.8 
22.6 
27.6 
24.1 

12.9 
16.1 

21.6 
22.1 

23.9 
14.8 
13.2 
22.2 
19.0 
21.4 

21.7 
27.4 

23.1 
36.2 

48.5 
53.6 
29.3 
49.6 
40.8 
47.0 

Bloomington  .  . 

Corn,  2d  year  on 
virgin  sod  

Sod  . 

Intermediate 
Intermediate 

Intermediate 
Intermediate 
Early  
Intermediate 
Intermediate 
Late 

Urbana  

Clover  

Potatoes  
Potatoes   

Urbana  

Urbana  

Potatoes  

Ontario  Parish 
Ontario  Parish 
Ontario  Parish 

Sod.  .  . 
Sod. 

Early  
Intermediate 
Late  . 

74.0 
77.0 
72.7 

81.4 
93.4 
78.7 

67.5 
71.3 
67.1 

69.5 
87.2 
68.5 

55.1 
59.0 
60.1 

41.8 
55.5 
47.5 

48.3 
53.9 
53.6 

33.5 
50.2 
38.9 

19.2 
17.4 
13.5 

36.0 
37.0 
29.6 

28.4 
24.4 
20.1 

51.8 
42.4 
43.2 

Sod  

Sod.    . 

Early 

Sod  

Intermediate 
Late  

Hopedale.  .  .  . 

Sod  

1923 

Bloomington  .  . 
Bloomington.  . 
Bloomington.  . 

Hopedale  

Alfalfa.  . 
Alfalfa   

Early  
Late  .... 

82.3 
94.6 
71.9 

67.4 

78.7 

66.1 
71.9 
68.6 

65.7 
70.0 
59.2 
56.3 
54.4 
48.4 

74.0 
83.3 
62.1 

53.9 
61.0 

57.5 
59.2 
55.9 

55.9 
60.3 
49.1 
49.3 
47.1 
41.4 

48.4 
80.1 
61.5 

40.2 
47.2 

26.6 
38.6 
56.3 

20.3 
36.1 
39.4 
21.7 
27.2 
36.5 

41.7 
69.9 
53.7 

25.6 
33.8 

22.7 
32.5 
45.7 

15.8 

27.8 
28.8 
18.3 
22.0 
30.2 

32.3 
13.4 

8.4 

28.3 
27.2 

34.8 
26.7 
10.2 

40.1 
32.5 
20.3 
31.0 
25.1 
11.2 

43.6 
16.1 
13.5 

52.5 
44.6 

60.5 
45.1 
18  2 

71.7 
53.9 
41.3 
62.9 
53.3 
27.1 

Barley  
Corn  

Intermediate 

Intermediate 
Late  

Hopedale  

Corn  

Ontario  Parish 
Ontario  Parish 
Ontario  Parish 

Urbana  
Urbana  

Corn  

Early  

Corn  

Intermediate 
Late 

Clover  
Clover      

Early  ....... 
Intewnediate 
Late  
Early  ....... 
Intermediate 
Late  

Urbana  
Urbana  
Urbana  
Urbana  

Clover  
3d  year  corn  
3d  year  corn  
3d  year  corn  

Mean  reduction  in  acre  yield  of  sound  corn  in  plots  planted  with  Diplodia-infected 
seed,  21.1  ±  1 . 009  bushels. 
21.1 

=  20.9.     Odds  greater  than  one  million  to  one. 

1.009 


351 


from  traces  to  as  much  as  43.  percent,  are  very  significant.  These 
data  show  that  seed  with  heavy  Fusarium  infection,  as  revealed  in  a 
properly  conducted  germination  test,  is  inferior  for  seed  purposes. 
Corn  grown  from  such  seed  usually  is  susceptible  to  injury  under 
unfavorable  weather  and  soil  conditions. 


CEPHALOSPORIUM-INFECTED   SEED 

The  economic  importance  of  the  black-bundle  disease  of  corn  has 
been  discussed  by  Reddy  and  Holbert.81  Undoubtedly  the  causal 
organism  (Cephalosporium  acremonium)  is  responsible  for  much  loss 
to  the  corn  crop,  altho  the  extent  of  the  damage  is  difficult  to  esti- 
mate accurately  at  the  present  time.  Experimental  data  on  the  be- 
havior of  corn  grown  from  good  seed  and  from  seed  infected  with 
Cephalosporium  acremonium  suggest  that  seed  infection  with  this 
organism,  under  some  conditions,  may  cause  a  very  material  loss  in 
the  corn  crop  (Table  40). 


from  seed primari/y  /ncrease  //?  yte/dofcorn 


Yield  of  corn 

infected  with  Dip/odia  zeae, 


from  goodseectoverseec/primarily 
infected  with  Dip/odia  zea  e 


I920\ 


1921  \ 


1922 


80       70       60       5O     40      30       2O       IO        0         IO       2O      30     4O      50 

Yield  in  Bushels  per  Acre 
CHART  21. — YIELDS  FROM  GOOD  SEED  AND  FROM  DIPLODIA-INFECTED  SEED  (Table  38) 

Under  like  conditions,  yields  of  corn  from  good  seed  always  are  higher  than 
those  from  Diplodia-infected  seed. 


352 


BULLETIN   No.   255 


[August, 


TABLE  39. — YIELDS  OF  DENT  CORN  GROWN  FROM  GOOD  SEED  AND  FROM 
FUSARIUM-INFECTED  SEED 


Year 

Location  of 
experiment 
(Illinois) 

Previous  crop 

Relative 
time  of 
planting 

Acre  yield 

Reduction  in 
sound  corn  fol- 
lowing use  of 
infected  seed 

Good  seed 

Fusarium-in- 
fected  seed 

Total 

Sound 

Total 

Sound 

1921 

31oomington.  . 

IJorn  
Corn  

Sarly  
intermediate 
intermediate 
Late  

bu. 
73.6 
69.5 
71.2 
82.7 
71.0 

50.2 

52.8 
59.0 

55.6 

75.8 
61.8 

100.0 

bu. 
52.3 
47.7 
47.5 
57.6 
48.5 

40.2 

46.5 

52.1 

48.2 
59.4 
54.6 

93.7 

bu. 
67.5 
62.8 
65.1 
74.7 
68.2 

39.2 

36.2 
52.0 

43.5 
74.2 
53.1 

98.2 

bu. 
44.4 
42.6 
42.0 
49.2 
33.5 

23.5 

30.7 
37.9 

34.1 
56.2 
40.6 

91.0 

bu. 
7.9 
5.1 
5.5 
8.4 
15.0 

16.7 

15.8 
14.2 

14.1 
3.2 
14.0 

2.7 

perct. 
15.1 
10.7 
11.6 
14.6 
30.9 

41.5 

34.0 
27.3 

29.3 
5.4 
25.6 

2.9 

Corn  

Late 

Corn  

Intermediate 

Intermediate 
Intermediate 

Intermediate 
Intermediate 
Late  

Corn  

Peoria  

Clover  

Clover  

Bloomington    . 

Corn,  2d  year  on 
virgin  sod  

Intermediate 

1922 

Girard  

Sod  

Intermediate 

Intermediate 
Intermediate 
Early  ....... 
Intermediate 
Intermediate 
Late 

74.2 

59.6 
35.0 
59.2 
58.3 
56.1 
53.0 

74.0 
77.0 
72.7 

81.4 
93.4 
78.7 

64.1 

49.3 
27.6 
45.0 
44.8 
46.6 
45.5 

67.5 
71.3 
67.1 

69.5 

87.2 
68.5 

68.4 

50.8 
30.5 
53.9 
51.5 
51.2 
50.6 

70.0 
73.2 
63.6 

71.5 
90.8 
74  0 

56.7 

37.7 
21.1 
40.3 
36.8 
41.4 
42.2 

63.3 
63.1 
60.2 

61.3 

78.8 
61.0 

7.4 

11.6 
6.5 
4.7 
8.0 
5.2 
3.3 

4.2 
8.2 
6.9 

8.2 
8.4 
7.5 

11.5 

23.5 
23.6 
10.4 
17.9 
11.2 
7.3 

6.2 
11.5 
10.3 

11.8 
9.6 
10.9 

Corn  

Potatoes  

Potatoes        

Ontario  Parish 
Ontario  Parish 
Ontario  Parish 

Hopedale  

Sod... 
Sod 

Early  
Intermediate 
Late   

Sod                  

Sod.  .  . 
Sod         

Early  ....... 
Intermediate 
Late  

Hopedale  

Sod  

1923 

Alfalfa    . 

Intermediate 
Late  

Intermediate 

Intermediate 
Late  

Early  
Intermediate 
Intermediate 
Late  

Early  .'  
Intermediate 
Intermediate 
Late  

95.5 
97.8 

73.1 

67.4 
78.7 

65.7 
68.9 
70.0 
59.2 

60.7 
60.1 
57.9 
51.4 

89  .  5 
88.4 

61.6 

53.9 
61.0 

55.9 
59.3 
60.3 
49.1 

52.6 

52.7 
50.4 
43.3 

93.4 
97.6 

69.6 

48.9 
60.3 

62.1 
65.8 
70.3 
56.9 

54.7 
49.6 
54.0 
50.3 

87.6 
79.6 

58.3 

30.7 
43.8 

51.9 

57.7 
62.6 
46.1 

47.2 
44.0 
47.2 
43.0 

1.9 

8.8 

3.3 

23.2 
17.2 

4.0 
1.6 
-2.3 
3.0 

5.4 
8.7 
3.2 
0.3 

2.1 
10.0 

5.4 

43.0 

28.2 

7.2 
2.7 
-3.8 
6.1 

10.3 
16.5 
6.3 
0.7 

Bloomington.  . 
Bloomington  .  . 

Hopedale  
Hopedale  

Alfalfa  
Barley  

Corn  
Corn  

Clover  
Clover  

Urbana  
Urhana  
Urbana  

Clover  
Corn     following 
clover  
Corn    following 
clover  

Urbana  

Corn    following 

Urbana  

Corn    following 
clover  

Mean  reduction  in  acre  yield  of  sound  corn  in  plots  planted  with  Fusarium-infected 
seed,  7.7  ±  0.58  bushels. 
7.7 

=  13.28.     Odds  greater  than  one  million  to  one. 

0.58 


1924} 


COKN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


353 


TABLE  40. — YIELDS  OF  YELLOW  DENT  CORN  FROM  GOOD  SEED  AND 
FROM  CEPHALOSPORIUM-!NFECTED  SEED 

Grown  at  various  points  in  central  Illinois,  1922  and  1923 


Year 

Character 
of  seed 

Number 
of 
experi- 
ments 

Mean  acre 
yield 

Reduction  following  use 
of  infected  seed 

Total 

Sound 

1922 
1923 

Good       

13 
13 

28 
28 

bu. 
59.8 

55.2 
61.3 
57.6 

bu. 
51.5 

45.9 
52.3 

48.7 

bu. 
5.6 

3.6 

perct. 
10.9 

6.9 

odds 
1110:1 

908:1 

Cephalosporium- 
infected 

Good         

Cephalosporium- 
infected  

EXTENT  OF  SEED  INFECTION  ON  ILLINOIS  FARMS 

The  extent  of  disease  infection  in  the  seed  corn  of  Illinois  again 
is  difficult  to  estimate  accurately.  However,  judging  from  the  many 
hundred  samples  that  have  been  sent  in  for  germination  tests,  both 
at  Urbana  and  Bloomington,  as  well  as  from  samples  secured  at  many 
corn  shows  during  the  past  two  years,  it  is  safe  to  say  that  the  larger 
part  of  the  seed  corn  being  used  thruout  the  state  is  more  or  less 
diseased.  Much  of  it  is  badly  diseased  and  produces  corn  very  sus- 
ceptible to  disease  infection  and  easily  injured  by  any  unfavorable 
soil  or  seasonal  condition.  A  comparatively  small  portion  of  it  is 
excellent  as  regards  viability,  vigor  in  germination,  and  freedom  from 
disease,  and  produces  corn  highly  resistant  to  disease.  The  percent- 
age of  good  seed  in  the  lots  examined  by  the  authors  during  the  past 
six  years  has  ranged  from  zero  to  as  much  as  90  percent,  varying 
with  the  year,  locality,  variety,  previous  selection  and  breeding,  and 
other  factors. 

ESTIMATE  OF  LOSSES  DUE  TO  CORN  DISEASES 

From  the  foregoing  data  and  discussion  it  must  be  realized  that 
it  is  exceedingly  hazardous  to  attempt  to  make  any  estimate  of  the 
combined  total  losses  due  to  all  the  diseases  under  discussion  in  this 
bulletin.  Holbert44  has  made  the  following  statement:  "Those  in 
close  touch  with  the  situation  feel  that  these  rots  are  cutting  the 
yields  of  corn  in  the  state  fully  15  percent. ' ' 

The  Office  of  Plant  Disease  Survey78  placed  the  loss  from  all  corn 
diseases  in  Illinois  at  13.5  percent  for  the  year  1921.  On  the  basis  of 
all  data  reported  in  this  bulletin,  as  well  as  on  the  basis  of  observations 
made  thruout  Illinois  for  a  period  of  years,  the  authors  feel  that  where 
inferior  and  infected  seed  is  used,  losses  to  the  corn  crop  from  dis- 
ease, including  smut  and  rust,  can  very  conservatively  be  placed  at 
20  percent. 


354  BULLETIN   No.   255  [August, 

PART  IV 

EXPERIMENTAL  CONDITIONS  AND  METHODS 
EXPERIMENTAL  PLOTS 

The  comprehensive  field  experiments  herein  reported  were  con- 
ducted principally  on  the  University  South  Farm  at  Urbana,  and  on 
the  Funk  Farms  at  Bloomington,  Illinois.  In  addition  to  the  many 
projects  conducted  at  these  two  places,  numerous  experiments  have 
been  located  and  supervised  in  various  localities  thruout  the  state 
(Fig.  54)  where  effective  cooperation  could  be  established  with  corn 
breeders,  farm  bureau  organizations,  and  other  agricultural  agencies. 
More  recently  a  number  of  the  University  of  Illinois  soil  fields  have 
been  used  for  the  cooperative  investigations  of  corn  diseases,  soil 
treatment,  and  soil  management  problems. 

,i' 
UNIVERSITY  SOUTH  FARM 

On  the  University  South  Farm  at  Urbana,  several  series  of  plots 
devoted  primarily  to  special  crop  production  experiments  are  laid 
out  to  show  the  effects  of  certain  soil  treatments,  such  as  the  applica- 
tion of  limestone  and  rock  phosphate.  Various  systems  of  crop  rota- 
tions are  employed  and  the  crops  are  so  handled  as  to  exemplify  the 
two  general  systems  of  farming,  grain  and  live-stock. 

Four  different  rotations  are  being  studied  on  these  fields.  The 
first,  designated  as  the  Northwest  rotation,  is  a  system  of  cropping 
in  which  the  alfalfa  remains  down  for  six  years  and  the  primary  part 
of  the  rotation,  comprizing  corn,  soybeans,  and  potatoes,  completes 
two  cycles  before  the  alfalfa  is  moved  to  another  field.  The  second, 
or  North-Central  rotation,  consists  of  corn,  corn,  spring  grains,  and 
clover.  This  represents  a  very  common  rotation.  The  third,  or 
South-Central  rotation,  consists  of  corn,  corn,  corn,  and  soybeans, 
and  should  be  regarded  as  an  undesirable  rotation  because  of  the 
three  years  of  corn.  The  fourth  is  known  as  the  Southwest  rotation 
and  is  considered  one  of  the  most  desirable  types.  It  is  a  four-crop 
system  consisting  of  wheat,  corn,  oats,  and  clover. 

The  general  soil  treatment  in  all  these  rotations  consists  of  rock 
phosphate,  crop  residues,  and  manures,  with  a  light  initial  application 
of  limestone. 

BLOOMINGTON  FIELDS 

Opportunity  was  afforded  on  the  Funk  Farms  for  selecting  field 
plots  from  a  very  wide  range  of  choice  sites.  The  areas  occupied  by 
these  various  field  experiments  ranged  in  size  from  a  small  plot  to 
as  much  as  30  acres,  depending  on  the  objects  of  the  particular  series 
of  experiments.  Previous  cropping  varied  from  native  grasses  on 


355 


virgin  prairie  sod  to  ground  on  which  there  had  been  continuous  corn 
for  seven  years.  Inasmuch  as  all  standard  rotations  of  the  corn  belt 
are  represented  on  these  farms,  it  has  been  possible,  in  practically 
every  instance,  to  outline  the  experiments  and  then  to  choose  suitable 
uniform  land  on  which  to  conduct  the  field  work.  The  soil  used  on 
the  Funk  Farms  was  of  the  brown  silt  loam  type.  All  cultural 
operations  on  the  experimental  plots  were  under  the  direct  supervision 
of  the  investigators. 

OUTLYING  FIELDS 

In  the  early  experiments  the  outlying  fields  (Fig.  54)  were  all 
located  on  uniform  soil  mostly  of  the  brown  silt  loam  type.  In  the 
more  recent  experiments,  however,  additional  representative  soil  types 
have  been  included.  Altho  the  outlying  fields  ^  did  not  receive  the 
constant  attention  that  was  given  the  experimental  plots  at  Urbana 
and  at  Bloomington,  they  were  well  supervised  and  it  is  believed  that 
the  data  from  these  fields  are 
reliable.  Where  there  was 
any  question  about  the  field 
technic  at  any  time  during 
the  season,  the  data  were 
discarded. 


SOIL  CONDITIONS 
The  term  "clean"  soil,  as 
used  in  this  bulletin  in  con- 
trast to  infested  soil,  refers 
to  such  ground  as  has  been 
cropped  neither  with  small 
grains .  that  were  scabby 
(Fusarium  head  blight)  nor 
with  corn  for  at  least  five 
years.  In  some  cases  the  land 
was  virgin  prairie  soil;  in 
other  cases  it  had  been  in  pas- 
ture for  a  period  of  years  or 
had  been  cropped  with  clover 
and  other  miscellaneous  crops. 
Such  soil  is  reasonably  free 
from  corn  disease  pathogenes. 
Whenever  the  terms  "clean" 
and  "infested"  soil  are  used 


FIG.  54. — LOCATION  OF  EXPERIMENTS 


35(5  BULLETIN   No.   255  [August, 

in  connection  with  experiments  discussed  in  this  bulletin,  the  spe- 
cific previous  cropping  is  mentioned  in  that  connection. 

STRAINS  OF  CORN  USED 

Varietal  names  of  the  different  strains  of  yellow  dent  corn  used 
in  the  experiments  herein  reported  have  been  avoided  purposely.  All 
the  strains  originally  came  from  Reid 's  Yellow  Dent.  It  is  well  known 
that  a  strain  of  corn  can  be  considered  to  be  the  same  strain  only  so 
long  as  it  is  selected  with  the  original  ideal  in  view.  Very  generally 
a  strain  loses  its  identity  soon  after  it  leaves  the  original  producer. 
Mr.  Reid  himself  changed  the  standard  of  his  yellow  dent  several  times 


FIG.  55. — MULTIPLE  TRAY  GERMINATOR  IN  OPERATION 

The  primary  purposes  of  the  germinator  are  to  show  the  pres- 
ence or  absence  of  disease  and  the  vigor  or  lack  of  vigor  of  the 
seedlings. 

during  his  lifetime.  During  the  first  thirty  years  of  his  work  he 
selected  for  a  rather  smooth,  horny  type,28'31  possessing  a  number  of 
those  ear  character  that  later  have  been  found  to  be  associated  with 
disease  resistance.  Later  he  was  overruled  by  other  members  of  the 
Illinois  Corn  Breeders '  Association,  who  were  confident  that  the  rough 
ear  was  a  better  and  more  profitable  ear  to  grow.  Mr.  Reid  reluctantly 
selected  toward  a  rougher  type  until  1909,  when  at  the  Illinois  Corn 
Breeders'  Association  Mr.  E.  D.  Funk28  presented  seven  years'  experi- 


19%4\  CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES  357 

mental  data  giving  concrete  proof  that  the  smoother  type,  under  his 
selection,  had  superior  yielding  ability.  It  is  said  that  Mr.  Reid 
danced  like  a  school  boy,  saying,  "I  told  you  so."  Mr.  Reid  imme- 
diately and  enthusiastically  went  back  to  growing  his  smoother  type, 
but,  unfortunately,  it  was  the  last  year  of  his  life. 

The  nearly  disease-free  seed  used  for  the  control  plots  in  these 
experiments  was  from  a  strain  of  corn  which  had  been  carefully 
selected  over  a  period  for  those  plant  and  ear  characters  that  have 
been  found  to  be  associated  with  productivity,  freedom  from  disease, 
and  disease  resistance.  These  characters  are  described  in  detail  else- 
wheTe  in  this  bulletin  under  "Value  of  Physical  Appearance  as  a 
Basis  for  Selection,"  page  431.  Other  strains  used  had  been  selected 
toward  somewhat  different  standards,  while  still  others  had  not  been 
selected  toward  any  definite  type.  Thus  it  has  been  deemed  advisable 
not  to  use  varietal  names,  which  in  most  cases  would  mean  nothing 
and  might  be  misleading.  However,  each  type  or  strain  used  in  the 
experimental  work  is  described  as  to  ear  characters  and  in  most  cases 
is  illustrated  by  a  typical  ear. 

GERMINATION  AND  SELECTION  OF  SEED 
DESCRIPTION  OF  GERMINATOR 

Seed  corn  for  all  the  experiments  reported  in  this  bulletin  was 
tested  for  viability  and  disease  symptoms  on  a  limestone-sawdust 
germinator,  a  development  of  the  table  germinator  described  by  Holbert 
and  Hoffer,47  which  was  used  in  the  tests  previous  to  1921.  The 
improvements  greatly  increased  the  capacity  of  the  germinator  but 
its  fundamental  principle  remained  the  same.  A  series  of  trays  made 
to  slide  into  an  upright  framework  takes  the  place  of  the  tables 
(Fig.  55).  These  trays  are  spaced  seven  inches  apart,  ten  trays  in 
an  upright  tier.  The  dimensions  of  each  tray  are  3  by  4i/£  feet  by 
2  inches  deep.  The  bottoms  of  the  trays  are  made  of  four  slats,  on 
which  strong  hardware  cloth  is  first  laid,  and  over  this  a  layer  of 
wire  mosquito  netting.  Well  leached  sawdust,  one  inch  deep,  is  then 
put  in  the  trays,  and  over  this  is  spread  just  enough  limestone  to 
cover  the  sawdust. 

A  sheet  of  heavy  unbleached  muslin  is  placed  on  each  of  the  trays 
of  the  germinator  just  before  putting  on  the  seed.  The  seed  is  covered 
with  a  lighter  piece  of  unbleached  muslin.  Before  the  muslins  are 
used  for  the  first  time  and  each  time  thereafter,  they  are  boiled  in 
water  for  an  hour  and  put  thru  a  clothes  wringer  just  before  using. 

With  such  a  large  extent  of  wet  surface  in  the  germinating  room, 
the  relative  humidity  is  very  high,  and  for  this  reason  the  burlap 
covering  which  on  the  old  table  germinator  was  used  in  addition  to 
the  muslin  is  dispensed  with.  The  trays  are  watered  three  times  daily 


358  BULLETIN   No.    255  [August, 

at  eight-hour  intervals.  A  fine  spray  nozzle  such  as  is  used  with 
power-spraying  machinery  is  connected  directly  with  a  city  water 
hydrant  and  gives  excellent  results.  The  water  passes  thru  a  large 
pressure  tank  located  in  the  germinator  room,  by  which  arrangement 
lukewarm  water  is  available  at  all  times  for  watering  the  trays.  Each 
test  is  continued  for  a  period  of  seven  days,  at  a  temperature  of  85°  F. 
An  automatic  thermostat  control  keeps  the  temperature  practically 
constant. 

TESTING  THE  EARS 

Ten  kernels  are  removed  in  a  spiral  from  Butt  to  tip  of  each  ear 
to  be  tested.  These  kernels  are  laid  out  in  a  straight  row  on  a 
germinator  tray  with  about  an  inch  space  between  kernels.  The  dis- 
tance between  rows,  however,  is  at  least  three  inches.  Each  test  is 
later  repeated  by  taking  another  ten  kernels  from  a  different  spiral 
on  the  same  ear.  In  some  of  the  experiments  herein  reported  each 
ear  was  tested  four  times,  making  a  total  of  forty  kernels  per  ear.  A 
slightly  different  technic  is  used  in  preparing  the  Diplodia  composites. 

In  making  the  germination  readings  the  factors  considered  are: 
viability ;  size  and  diameter  of  plumule ;  number,  length,  and  branch- 
ing of  roots;  presence  of  parasitic  fungi;  and  extent  of  rotting 
caused  by  these  fungi. 

The  term  viability,  as  used  in  this  bulletin,  refers  to  the  ability  to 
germinate  and  grow  regardless  of  the  kind  of  growth. 

SELECTION  or  SEED 

Each  year  germination  tests  were  made  of  many  hundred  ears, 
and  on  the  basis  of  these  tests  a  large  number  of  ears  were  selected 
to  represent  the  various  kinds  of  infected  ears  and  the  nearly  dis- 
ease-free ears.  These  groups  of  ears  were  known  as  composites,  and 
from  them  seed  packets  were  made  according  to  the  outline  of  the 
experiments  of  that  season.  These  packets  were  made  up  so  that 
each  contained  the  same  number  of  kernels  from  each  ear  in  its 
respective  composite.  Following  is  a  discussion  of  these  various 
composites. 

GOOD-SEED  COMPOSITES 

Ears  of  which  the  germinated  kernels  produced  strong  plumules 
of  good  diameter  and  an  abundant,  vigorous  root  system,  and  which 
showed  a  bright  external  appearance  of  the  kernels  with  no  sign  of 
discoloration  when  the  kernels  were  cut  lengthwise  thru  the  middle, 
were  classed  as  nearly  disease-free  ears.  The  viability  on  the 
germinator  was  always  100  percent  (Fig.  1  and  Plate  I).  The  term 
' '  nearly ' '  is  used  because  some  types  of  infection  perhaps  may  escape 
detection  on  the  germinator,  and  furthermore,  infection  in  slight  forms 
may  sometimes  be  local  on  an  ear,  and  the  infected  section  may  not 


1924]  CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES  359 

be  represented  by  any  of  the  kernels  tested.  Unless  otherwise  speci- 
fied, the  nearly  disease-free  seed  was  selected  from  apparently  disease- 
free  plants  and  possessed  those  physical  characteristics,  later  herein 
described,  that  were  found  to  be  associated  with  freedom  from  dis- 
ease and  disease  resistance.  In  this  bulletin  the  term  "good  seed" 
is  used  synonymously  with  the  term  "nearly  disease-free  seed." 

SCUTELLUM  ROT  COMPOSITES 

The  scutellum  rot  composites  were  made  up  of  ears  that  had  57 
to  70  percent  of  the  kernels  scutellum-rotted  on  the  germinator  (Fig.  2 
and  Plate  I),  and  only  traces  of  Fusarium  moniliforme  and  Diplodia 
zeae  infection.  The  viability  on  the  germinator  was  from  95.5  to  100 
percent.  i 

FUSARIUM-INFECTED  COMPOSITES* 

The  Fusarium-infected  composites  were  made  up  of  ears  ranging 
from  57  to  92  percent  in  Fusarium  infection  (Fig.  22  and  Plate  I), 
but  showing  no  Diplodia  infection  and  only  traces  of  scutellum  rot. 
The  viability  was  from  97  to  98  percent. 

CEPHALOSPORIUM-INFECTED    COMPOSITES 

The  Cephalosporium-infected  composites  ranged  from  65  to  95 
percent  in  infection  and  from  99  to  100  percent  in  viability.  The 
seedlings  had  a  good  appearance  on  the  germinator  and  might  have 
been  passed  as  nearly  disease-free  seed  by  an  inexperienced  person. 
It  is  true  that  when  this  fungus  grows  on  kernels  in  conjunction  with 
other  organisms  such  as  Fusarium  moniliforme,  Diplodia  zeae,  or 
Khizopus  spp.,  it  easily  escapes  detection  by  the  usual  macroscopic 
examination.  However,  the  Cephalosporium  composites  used  in  these 
experiments  were  made  up  of  ears  selected  by  microscopically  examin- 
ing germinating  kernels  and  choosing  ears  that  were  infected  with  this 
organism  only. 

DIPLODIA-INFECTED   COMPOSITES 

A  slightly  different  technic  was  used  in  preparing  the  Diplodia- 
infected  composites.  In  the  previously  described  composites  the  ear 
was  considered  the  unit,  and  the  whole  ear  was  either  used  or  rejected. 
Ears  severely  infected  with  Diplodia  cannot  be  used  for  field  experi- 
ments because  the  kernels  are  dead.  Slightly  infected  ears  generally 
show  three  successive  zones  when  tested  on  the  germinator :  first,  there 
may  be  a  portion  in  which  infection  has  progressed  to  such  an  extent 
that  the  kernels  are  dead;  next,  there  is  a  zone  that  is  infected  but 
still  viable;  and,  third,  there  may  be  an  uninfected  zone  (Fig.  56). 
Ears  which  showed  the  presence*  of  Diplodia  zeae  when  given  a 
germination  test  in  the  usual  manner  were  retested  by  taking  ten 


360  BULLETIN   No.   255  [August, 

kernels  in  a  straight  row  from  opposite  sides  of  each  ear  (Fig.  56) 
and  placing  these  kernels  in  two  parallel  rows  on  the  germinator.  By 
this  method  it  was  determined  whether  infection  and  zonation  were 
uniform  around  the  circumference  of  the  ears.  The  kernels  from  the 
zones  that  were  dead  and  also  those  from  the  zones  that  were  not 
infected  were  then  removed  and  the  remainder  were  used  in  preparing 
the  Diplodia-infected  composites. 

The  Diplodia-infected  composites  ranged  from  64  to  86  percent  in 
infection  with  Diplodia  zeae  and  from  87  to  92  percent  in  viability. 

MODERATELY   DISEASED    COMPOSITES 

In  data  obtained  from  the  experiments  up  to  and  including  1920, 
the  term  ' '  moderately  diseased ' '  is  used.  The  diseases  concerned  were 
principally  of  the  scutellum-rot  type  but  there  was  some  Fusarium, 
Diplodia,  Cephalosposium,  and  perhaps  other  infections.  In  none  of 
the  seed  lots,  however,  was  the  proportion  of  infected  kernels  greater 
than  50  percent,  and  in  every  case  the  viability  was  99  percent  or  over. 

HORNY    AND    STARCHY    COMPOSITES 

The  horny  composites  were  made  up  of  corn  that  showed  three- 
fourths  or  more  of  each  kernel,  as  viewed  on  the  side  opposite  the 
germ,  to  be  of  horny  composition  (Plate  IV).  The  starchy  composites 
wrere  made  up  of  corn  that  showed  half  or  more  of  each  kernel,  when 
examined  in  a  similar  way,  to  be  starchy. 

The  term  "horny,"  as  used  in  this  bulletin,  refers  to  the  corneous 
starchy  portion  of  the  endosperm.  The  term  "starchy"  refers  to  the 
soft,  white  starchy  portion  found  mostly  in  the  crown  portion  of  the 
endosperm.  The  horny  part  is  more  translucent  than  the  starchy 
portion  and  in  yellow  corn  is  of  a  much  deeper  shade.  It  is  well 
known,  of  course,  that  neither  portion  is  purely  starch.  Hopkins, 
Smith,  and  East50  have  reported  in  detail  on  the  structure  and  com- 
position of  the  corn  kernel,  and  their  data  show  that  the  horny  portion 
is  richer  in  protein  than  the  soft,  starchy  portion,  while  the  latter 
has  a  higher  percentage  of  ash. 

PLANTING  AND  CULTURAL  METHODS 

All  plots  except  those  at  Urbana  were  planted  in  hills  42  inches 
apart  each  way,  and  except  in  a  few  cases,  at  the  rate  of  three  kernels 
per  hill.  At  Urbana  they  were  planted  in  hills  40  inches  apart  each 
way  and  at  the  rate  of  two  kernels  per  hill.  To  insure  an  accurate 
drop,  all  plantings  were  made  by  means  of  specially  designed  hand 
planters,  having  a  funnel  at  the  top  and  a  tube  leading  to  the  outlet. 

The  usual  size  of  these  plots  was  4  rows  wide  by  10  hills  long. 
Alternate  with  every  plot  planted  with  infected  or  inoculated  seed 


CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES 


361 


was  a  plot  of  the  same  size  planted  with  nearly  disease-free  check  seed, 
or  uninoculated  seed.  These  were  replicated  a  number  of  times,  in 
most  cases  a  large  number  of  times,  so  that  some  experiments  numbered 
420  individual  plots. 

The  stand  was  not  thinned  or  tampered  with  in  any  way.    No  seed 
was  used  that  did  not  have  a  very  high  percentage  of  germination. 


FIG.  56. — PREPARATION  OF  DIPLODIA-INFECTED  SEED  COMPOSITE 

(Above)  Diplodia-infected  ear,  showing  manner  in  which  kernels  are  taken 
out.  A  similar  row  is  taken  out  on  the  opposite  side  of  the  ear,  and  both  sets  of 
kernels  are  germinated  at  the  same  time.  The  row  of  germinated  kernels 
shows  that  the  tip  half  of  the  ear  is  infected.  (Center)  An  enlarged  view  of 
ten  of  the  kernels  from  this  ear.  (Below)  The  part  of  this  ear  that  is  used 
in  the  Diplodia-infected  composite.  The  butt  half  was  taken  off  because  it 
showed  no  infection,  and  the  tip  was  removed  because  infection  had  progressed 
to  the  point  where  the  kernels  would  not  germinate. 


362 


BULLETIN   No.   255 


[August, 


One  of  the  effects  of  corn  disease  is  an  increased  percentage  of  weak 
and  blighted  plants.  By  planting  thick  and  later  thinning  out  the 
weak  plants  a  disproportional  part  of  the  diseased  plants  is  eliminated, 
thereby  partly  controlling  the  disease.  As  such  a  method  of  control  is 
worthless  to  the  corn  grower  in  the  corn  belt  because  it  could  not  be 
put  into  practical  operation,  it  was  avoided  in  all  experiments  where 
yield  data  were  to  be  obtained. 

Great  care  was  exercised  thruout  the  season  to  avoid  mechanical 
injury  to  the  plants  during  cultivation,  and  to  guard  against  insect 
pests  and  rodents.  Whenever  there  was  any  appreciable  amount  of 
damage  due  to  any  of  these  causes,  that  part  of  the  experiment  or  the 
whole  experiment,  as  the  case  happened  to  be,  was  discarded. 

HARVESTING  METHODS 

In  all  the  experiments  the  entire  population  from  each  plot  was 
harvested.  In  several  experiments  the  outer  two  rows  of  each  plot 
were  harvested  separately  in  an  attempt  to  determine  the  border 
effect.  As  the  stand  was  fairly  even  in  all  the  plots,  the  border  effect 
was  either  lacking  or  very  small  and  was  insignificant  in  view  of  the 
probable  errors  involved  (Table  42).  Therefore  it  was  deemed 
advisable  to  use  the  entire  yield  rather  than  the  yield  of  the  central 
rows  only,  as  the  advantages  gained  in  accuracy  by  working  with 
a  larger  population  more  than  offset  any  border  effect  that  may  have 
occurred. 

When  the  corn  was  harvested  it  was  put  into  open-meshed  onion 
bags  and  the  bags  were  sewed  up.  These  were  then  taken  into  a  warm 
building  and  placed  on  a  frame  of  slats  at  some  distance  from  the 
floor  to  allow  free  circulation  of  air.  Later  in  the  season  the  corn 
was  separated  into  marketable  and  unmarketable  grades,  and  shelled. 

TABLE  41. — BORDER  EFFECT  IN  CORN  PLOTS,  BLOOMINGTON,  1921 

Four  rows  were  planted  in  each  plot  and  every  alternate  plot  was  planted  with 
nearly  disease-free  seed.  The  yields  from  the  outer  and  the  inner  rows  were 
weighed  separately. 


Ex- 
peri- 
ment 

Condition 
of  seed 

Number 
of 
repli- 
cations 

Acre  yield 

Difference 

Difference 

Outer 
two  rows 

Inner 
two  rows 

Probable 
error 

A 
B 

Nearly  disease- 
free  

10 
10 

9 
9 

bu. 
99.9  +  1.5 

82.7  ±  1.0 

100.3  ±  1.3 
80.3  ±  1.8 

bu. 
97.1  ±  1.0 
83.0  +  1.6 

98.0  +  1.6 

78.8  ±  1.0 

bu. 
2.8  ±  1.8 
0.3  +  1.9 

2.3  +  2.1 
1.5  +  2.0 

1.6 
0.2 

1.1 
0.7 

Moderately  dis- 
eased   

Nearly  disease- 
free  

Moderately  dis- 
eased   

1924]  CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES  363 

Its  moisture  percentages  were  then  determined,  and  the  yields  calcu- 
lated on  the  basis  of  shelled  corn  reduced  to  a  uniform  moisture 
content.  Exceptions  were  made  in  the  case  of  some  of  the  outlying 
experiments  in  other  parts  of  the  state  where  this  procedure  could  not 
be  followed.  In  these  cases  the  experiments  were  harvested  rather 
late  in  the  season  when  the  ears  had  dried  considerably,  and  yields  were 
based  on  the  air-dry  weight  of  ear  corn. 

Beginning  with  1920,  all  yields  were  separated  into  marketable 
(sound)  and  unmarketable  grades.  This  technic  is  illustrated  and 
described  in  detail  by  Holbert  et  al.is  The  unmarketable  grade  in- 
cluded sound  nubbins  less  than  half  the  length  of  a  normal-sized  ear 
for  the  variety,  or  larger  ones  that  were  poorly  filled,  ears  or  nubbins 
with  an  appreciable  amount  of  ear  rot,  and  chaffy  ears  or  nubbins. 
There  is  usually  a  higher  percentage  of  unmarketable  corn  in  the  yields 
from  diseased  seed  than  from  disease-free  seed.  Unless  this  separation 
is  made,  therefore,  the  differences  in  the  economic  values  of  the  yields 
often  are  not  shown  by  the  data. 

STATISTICAL  ANALYSIS 

Hall  and  Russell34  state  that  "an  experiment  may  be  defined  as  a 
question  put  to  Nature;  but  tho  we  may  say  that  Nature  never  lies, 
that  is  only  true  in  so  far  as  we  have  put  the  right  question  and 
interpreted  the  answer  correctly. "  If  it  is  assumed  that  in  the  experi- 
ments reported  in  this  bulletin  the  right  question  has  been  put,  then 
the  correctness  of  the  answer  sought  from  nature  will  hinge  on  the 
interpretation  of  the  results  obtained. 

In  field  trials  it  is  common  experience  to  find  considerable  variation 
in  yields  of  plots  given  the  same  treatment  or  planted  to  the  same 
variety,  due  mainly  to  variation  in  soil.  For  this  reason,  more  accurate 
comparisons  are  made  if  the  test  with  the  variety  or  treatment  is 
replicated,  for  of  course  an  average  of  several  results  is  much  nearer 
the  truth  than  any  single  result.  The  more  numerous  the  replications, 
the  more  justification  for  applying  the  statistical  method  to  their 
yields. 

The  interpretation  of  experimental  results  is  concerned  with  the 
significance  or  non-significance  of  differences  in  the  results  obtained 
from  the  treatments  or  varieties  under  comparison.  In  dealing  with 
variables,  we  must  necessarily  deal  with  a  large  number  of  causes  that 
bring  about  variation.  If,  in  a  field  experiment,  all  causes  of  varia- 
tion could  be  removed  so  that  any  differences  obtained  would  be  due 
wholly  to  the  factor  being  tested,  interpretation  of  the  results  would 
of  course  be  clear  and  unmistakable.  So  many  external  causes,  how- 
ever, are  constantly  at  work  to  bring  about  variation  that  uncertainty 
always  exists  regarding  the  correct  interpretation  of  the  results.  The 


364  BULLETIN   No.    255  [August, 

determination  of  the  probable  error  is  believed  to  remove  this  uncer- 
tainty to  a  large  extent. 

The  probable  error  is  an  expression  of  the  reliance  that  can  be 
placed  in  the  results  of  an  experiment.  In  the  words  of  Babcock  and 
Clausen3  the  probable  error  "is  an  arbitrary  term  used  to  denote  the 
amount  that  must  be  added  to  or  subtracted  from  the  observed  value 
to  obtain  two  limiting  figures  of  which  it  may  be  said  that  there  is  an 
even  chance  that  the  true  value  lies  within  or  without  these  limits." 
Such  limiting  figures  include  approximately  one-half  of  the  distribu- 
tion. If  twice  the  probable  error  be  added  to  or  subtracted  from  the 
observed  value,  the  chances  that  the  true  value  lies  within  rather  than 
outside  these  limits  increases  to  4 : 1 ;  and  with  three  times  the  prob- 
able error,  to  21 : 1.  In  this  bulletin  a  result  which  differs  from  the 
observed  value  by  3.2  (or  more)  times  the  probable  error  is  regarded 
as  significant. 

The  probable  errors  given  in  this  bulletin  were  calculated  by  the 
following  formula,  except  where  otherwise  indicated: 

E=  ±0.8453 


where  2V  is  the  sum  of  the  variations  from  the  mean,  and  N  the 
number  of  variates.  This  is  commonly  known  as  Peter's  formula. 
It  is  preferred  to  Bessel's  formula, 

E  =  ±0.6745  A  SV2 

\N(N  — 1)  ' 

because  there  is  a  considerable  saving  of  time  in  making  the  calcula- 
tions. Furthermore,  the  values  of  E  obtained  by  the  two  formulas 
are  practically  the  same. 

When  it  is  desired  to  compare  two  values  (as  means  or  standard 
deviations),  each  with  its  own  probable  error,  the  difference  between 
thjem  is  first  determined  and  the  probable  error  of  this  difference  calcu- 
lated by  the  formula — 

E  of  difference  =  ± 


where  Ea  is  the  probable  error  of  one  of  the  values  under  comparison, 
and  Eb  is  the  probable  error  of  the  other.  The  difference  is  then 
divided  by  the  probable  error  of  the  difference  to  determine  how  many 
times  greater  the  former  is  than  the  latter.  If  this  quotient  is  as  much 
as  3.2  or  greater,  the  difference  between  the  values  under  comparison 
is  considered  great  enough  to  be  significant.  The  odds  of  probability 

Difference 

corresponding  to  the  quotients  ^  -  are  given  in  Table  41. 

E  of  Difference 

An  example  will  make  the  application  clear.  In  Table  6  in  the 
planting  of  May  14,  two  yields  are  given — 66.3  ±  1.2  and  52.9  ±  3.0 
bushels.  The  difference  between  these  two  yields  is  13.4  bushels  and 
the  probable  error  of  this  difference  is  3.2  bushels.  The  difference, 


1924] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


365 


13.4,  is  four  times  the  probable  error  of  the  difference,  3.2,  and  hence 
is  sufficiently  great  in  comparison  with  the  probable  error  of  this  ex- 
periment to  justify  the  conclusion  that  this  increase  in  yield  is  due 
to  real  superiority  in  yielding  ability  and  not  to  favorable  location 
in  the  field,  so  far  as  such  factors  as  soil  fertility  or  soil  moisture  are 
concerned. 

A  number  of  experiments  reported  in  this  bulletin  are  concerned 
with  the  comparison  of  good  seed  with  seed  infected  with  any  one  of 
the  several  organisms  causing  corn  root,  stalk,  and  ear  rots.  These 
experiments  have  been  conducted  at  different  locations  during  the 
same  year  and  in  different  years.  Obviously  the  variations  in  yield 
of  good  seed  or  diseased  seed  under  these  conditions  are  not  such  as 
can  be  treated  by  the  method  just  described*  There  are  two  ways  of 
treating  such  data,  as  Love64  has  pointed  out.  In  one,  the  differences 
can  be  calculated  for  paired  plots,  and  the  probable  error  of  these 
differences  determined  by  Bessel's  formula  in  the  usual  way.  The 

TABLE  42. — PROBABILITY  OF  OCCURRENCE  OF  STATISTICAL  DEVIATIONS  OF 
DIFFERENT  MAGNITUDES  RELATIVE  TO  THE  PROBABLE  ERROR 


Deviation 
divided  by 
probable 
error 

Probable  oc- 
currence of  a 
deviation  as 
great  as  or 
greater  than 
e  designated 
one  in  100 
trials 

Odds  against 
the  occurrence 
of  a  deviation 
as  great  as  or 
greater  than 
the  designated 
one 

Deviation 
divided  by 
probable 
error 

Probable  oc- 
currence of  a 
deviation  as 
great  as  or 
greater  than 
the  designated 
one  in  100 
trials 

Odds  against 
the  occurrence 
of  a  deviation 
as  great  as  or 
greater  than 
the  designated 
one 

1.0 

50.00 

1.00  to  1 

3.5 

1.82 

53.95  to  1 

1.1 

45.81 

1  .  18  to  1 

3.6 

1.52 

64.79  to  1 

1.2 

41.83 

1  .  39  to  1 

3.7 

1.26 

78.37  to  1 

1.3 

38.06 

1  .  63  to  1 

3.8 

1.04 

95.15  to  1 

1.4 

34.50 

1  .  90  to  1 

3.9 

0.853 

116.  23  to  1 

1.5 

31.17 

2.21  to  1 

4.0 

0.698 

142.  26  to  1 

1.6 

28.05 

2.  57  to  1 

4.1 

0.569 

174.75  to  1 

1.7 

25.15 

2  .  98  to  1 

4.2 

0.461 

215.92  to  1 

1.8 

22.47 

3  .  45  to  1 

4.3 

0.373 

267.  10  to  1 

1.9 

20.00 

4.  00  to  1 

4.4 

0.300 

332.33  to  1 

2.0 

17.73 

4.64  to  1 

4.5 

0.240 

415.  67  to  1 

2.1 

15.67 

5  .  38  to  1 

4.6 

0.192 

519.  83  to  1 

2.2 

13.78 

6.26  to  1 

4.7 

0.152 

656  .  89  to  1 

2.3 

12.08 

7.  28  to  1 

4.8 

0.121 

825  .  45  to  1 

2.4 

10.55 

8.  48  to  1 

4.9 

0.095 

1  051.63  to  1 

2.5 

9.18 

9.89  to  1 

5.0 

0.074 

1  350.35  to  1 

2.6 

7.95 

11.58  to  1 

6.0 

0.0052 

19  230.  00  to  1 

2.7 

6.86 

13  .  58  to  1 

7.0 

0.00023 

434  782.  00  to  1 

2.8 

5.90 

15.95  to  1 

8.0 

0.000000068 

1  470  588  234.  00  to  1 

2.9 

5.05 

18.  80  to  1 

3.0 

4.30 

22  .  26  to  1 

3.1 

3.65 

26  .  40  to  1 

- 

3.2 

3.09 

31.36  to  1 

3.3 

2.60 

37  .  46  to  1 

3.4 

2.18 

44  .  87  to  1 

366  BULLETIN   No.    255  [August, 

mean  difference  divided  by  the  probable  error  of  this  difference  gives 
a  quotient,  from  which  the  odds  can  be  readily  interpolated  from 
Table  42  (Pearl  and  Miner).77  In  the  other  way  of  treating  such 
data,  a  method  known  as  Student's100  can  be  used.  In  this  method 
the  individual  differences  between  the  paired  items  are  determined  as 
above,  and  squared;  the  sum.  of  the  squares  is  then  divided  by  the 
number  of  differences,  and  from  the  quotient  the  square  of  the  mean 
difference  is  subtracted.  The  square  root  of  the  remainder  is  the 
standard  deviation  (Grindley  and  Mitchell).32  The  next  step  is  to 
find  the  value  Z,  which  is  the  ratio  between  the  mean  deviation  and 
the  standard  deviation.  Student101  has  computed  a  table  of  prob- 
abilities for  values  of  Z  for  any  number  of  differences  from  2  to  30, 
and  from  this  table  the  odds  that  the  difference  between  the  plots 
compared  is  large  enough  to  be  significant  can  be  readily  interpolated. 
Odds  of  30  to  1  or  better  are  accepted  in  this  bulletin  as  indicating 

significant  gain  or  reduction. 

\ ' 

PART  V 

PHYSICAL   CHARACTERS  OF  SEED  EARS  ASSOCIATED 
WITH  SEED  INFECTION  AND  NONINFECTION 

EARLY  WORK  ON  THE  GERMINATOR  TO  DETECT 
NONINFECTION  AND  SUPERIOR  VIGOR 

During  the  earlier  years  of  the  investigations  reported  in  this 
bulletin,  it  was  the  privilege  of  the  senior  author  to  supervise  the 
selection  and  germination  of  many  thousands  of  bushels  of  seed  corn 
for  Mr.  Eugene  D.  Funk.  At  that  time  the  principal  objective  was 
to  find  any  relation  that  might  exist  between  the  appearance  of  corn 
on  the  germinator  and  its  performance  in  the  field.  Many  experi- 
ments were  conducted  that  gave  nothing  of  value.  Others,  however, 
suggested  lines  of  attack  that  have  since  proved  very  productive. 

PERFORMANCE  OF  GERMINATOR- SELECTED  EARS 

During  the  winter  of  1915-1916,  fifty  ears  were  selected  irrespec- 
tive of  physical  appearance  but  the  kernels  from  which  were  the  most 
vigorous  and  most  nearly  disease-free  on  the  germinator.  These  fifty 
ears  probably  represented  the  best  germinating  ears  out  of  more  than 
one  hundred  thousand  ears  tested  at  that  time.  The  fifty  ears  were 
then  retested  and  only  the  superior  half  of  them  were  saved.  The 
following  spring  these  twenty-five  carefully  selected  seed  ears  were 
included  in  experiments  along  with  more  than  a  thousand  ears  of 
fancy  appearance  which  were  prized  highly  on  account  of  their  size, 
symmetry,  and  uniformity  of  type.  The  thousand  ears  had  been 
germinated  to  determine  viability  only.  No  attempt  had  been  made 
to  eliminate  those  ears  which  showed  a  moldy  condition  on  the  germi- 


1924} 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


367 


nator,  since  at  that  time  this  condition  was  not  known  to  be  par- 
ticularly significant. 

Much  to  the  surprise  of  the  investigators,  the  corn  grown  from 
the  twenty-five  ears  selected  on  the  basis  of  vigor  of  germination 
and  freedom  from  infection,  as  well  as  viability,  proved  to  be  superior 
in  both  yield  and  quality  to  the  corn  grown  from  the  seed  ears 
selected  on  the  basis  of  appearance. 

These  experiments  were  repeated  the  following  year  with  a  much 
larger  number  of  ears  from  different  sources  representing  several 
standard  varieties  of  field  corn.  Results  again  were  decidedly  in  favor 
of  corn  selected  from  the  germinator  on  the  basis  of  vigor  and  free- 
dom from  disease,  as  well  as  viability.  A  few  'of  these  original  germi- 
nator-selected  ears  are  shown  in  Fig.  57. 


FIG.  57. — EARS  SELECTED  ON  THE  BASIS  OF  PERFORMANCE  ON 

THE  GERMINATOR 

The  corn  grown  from  ears  selected  on  the  basis  of  germina- 
tion and  freedom  from  infection,  as  well  as  viability,  on  the 
germinator,  proved  to  be  superior  in  both  yield  and  quality  to 
the  corn  grown  from  the  seed  ears  selected  on  the  basis  of 
appearance. 


368  BULLETIN   No.    255  [August, 

PHYSICAL  APPEARANCE  OF  GERMINATOR-SELECTED  EARS 

Much  to  the  disappointment  of  the  investigators,  at  that  time,  the 
seed  ears  selected  on  the  basis  of  their  germination  record  were  any- 
thing but  ideal  from  the  standpoint  of  conformity  to  commonly  rec- 
ognized standards.  The  ears  were  of  mid-smooth  to  smooth  indenta- 
tion and  possessed  bright  kernels  of  horny  composition.  They  also 
were  decidedly  smaller  in  circumference  in  proportion  to  length  than 
the  ears  that  had  been  selected  up  to  that  time  for  breeding  purposes. 

RELATION  OF  GENERAL  APPEARANCE  OF  SEED 
EARS  TO  SEED  CONDITION 

As  a  result  of  the  various  experiments  with  healthy  and  diseased 
corn,  both  in  the  field  and  in  the  laboratory,  it  was  noted  that  certain 
physical  characters  of  seed  ears  were  correlated  with  certain  per- 
formances on  the  germinator  and  in  the  field.  , ,  In  1919-1920  an  ex- 
periment was  conducted  to  determine  more  definitely  the  relation  be- 
tween the  physical  appearance  of  seed  ears  and  their  infection  or  free- 
dom from  infection.  Approximately  600  ears  of  yellow  dent  corn 
which  had  been  carefully  selected  in  the  field  from  good  stalks  and 
stored  on  racks,  were  classified  on  the  basis  of  their  physical  appear- 
ance as  apparently  good  or  apparently  diseased.  These  ears  then 
were  germinated  under  uniform  conditions.  At  the  end  of  the  germi- 
nation test  they  were  reclassified  on  the  basis  of  their  record  on  the 
germinator  (Table  43).  Of  the  ears  that  had  been  classed  as  ap- 
parently good,  86.9  percent  proved  to  be  relatively  disease-free  on  the 
germinator,  while  of  the  ears  that  had  been  classed  as  apparently 
diseased,  only  37.9  percent  proved  to  be  relatively  disease-free  on 
germination. 

The  above  results  led  to  a  more  critical  study  of  the  physical 
characteristics  of  a  large  group  of  ears  classified  on  the  basis  of  the 
germinator  test,  as  diseased,  moderately  diseased,  and  disease-free. 


TABLE  43. — EFFECTIVENESS  OF  SELECTING  SEED  CORN  ON  THE  BASIS  OF  PHYSICAL 
APPEARANCE  AS  DETERMINED  BY  LATER  TESTS  ON  THE  GERMINATOR 

All  ears  were  selected  from  good  mother  plants  and  properly  stored  in  the  fall  of 
1919.     Germination  tests  were  made  in  the  spring  of  1920. 


Ear  classification  on  basis  of 
physical  appearance 


Ear  classification  on  the  basis  of 
germination  record 


Relatively 
disease-free 


Diseased 


Apparently  good  .  .  . 
Apparently  diseased . 


perct. 
86.9 

37.9 


perct. 
13.1 

62.1 


1924]  CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES  369 

These  studies  are  reported  in  Tables  44  to  50.  No  ears  were  included 
in  the  diseased  groups  that  did  not  have  high  viability.  The  80  ears 
reported  in  Table  44  were  selected  from  2,500  ears  that  were  tested 
regardless  of  physical  appearance.  The  95  ears  reported  in  Table 
45  were  selected  from  approximately  1,000  ears.  Ears  reported  in 
Table  47  and  48  were  those  from  which  nearly  disease-free  seed  com- 
posites and  the  composites  primarily  affected  with  scutellum  rot  were 
made  for  1920,  1921,  and  1922.  Of  the  diseased  ears  the  percentages 
of  kernels  affected  with  scutellum  rot  on  the  germinator  in  the  three 
respective  years  were  26.4,  50.6,  and  57.  Of  the  nearly  disease-free 
composites,  the  percentages  of  affected  kernels  were  1.3,  3.5,  and  4.6 
percent,  respectively.  The  viability  in  the  case  of  the  nearly  disease- 
free  ears  was  100  percent  thruout  the  three  years.  These  ears  showed 
no  evidence  of  either  Fusarium  or  Diplodia  infection. 

Ears  whose  physical  characteristics  and  laboratory  germination  rec- 
ords are  given  in  Tables  49  and  50,  comprized  the  Fusarium-infected, 
Diplodia-infected,  and  good-seed  composites  used  in  the  many  experi- 
ments thruout  the  state  under  the  supervision  of  the  authors  in  1921 
and  1922.  They  were  all  from  the  same  strain  of  corn.  For  the  most 
part,  the  ears  had  been  selected  in  the  field  from  desirable  plants. 
Fig.  67  illustrates  the  appearance  of  a  few  representative  ears  from 
which  the  good-seed  composites  planted  in  1921  were  made. 

Of  the  many  characters  recorded  and  studied,  those  in  which  the 
disease-free  ears  differed  most  consistently  from  ears  known  to  be 
infected  were:  (1)  luster  of  ear,  (2)  shank  attachment,  or  nature  of 
butt  of  cob,  (3)  characteristics  of  tip  of  ear,  (4)  type  of  kernel 
indentation,  (5)  nature  of  endosperm,  and  (6)  luster  of  kernel. 

LUSTER  OF  EAR 

Disease-free  ears  of  good  viability  and  vigor  that  have  matured 
normally  on  healthy  plants  have  a  bright,  rich  luster.  On  the  other 
hand,  ears  that  have  come  from  root-rotted  and  stalk-rotted  plants 
usually  present  a  dry,  dull  appearance  after  curing.  This  difference 
in  luster  is  particularly  apparent  when  disease-free  and  diseased  ears 
are  compared  side  by  side.  Considerable  experience  in  comparing  ears 
known  to  be  infected  and  ears  known  to  be  free  from  infection  is 
necessary  to  fix  the  proper  standard  of  luster  in  the  mind  of  the 
worker,  but  when  once  established,  this  difference  in  physical  appear- 
ance may  be  used  to  great  advantage  as  one  determining  factor  in  the 
selection  of  seed  corn. 

SHANK  ATTACHMENT 

The  shank  is  a  very  important  organ  of  the  corn  plant.  It  not  only 
supports  the  ear  but  is  the  structure  thru  which  food  materials  are 
conducted  to  the  ear.  Surrounded  by  both  leaf  sheath  and  husks,  it 


370 


BULLETIN   No.   255 


[August, 


FIG.   58. — BROKEN   AND   ROTTED   SHANKS 

When  weakened  by  local  rotting,  the  shank  often  breaks  or 
crumples  under  the  weight  of  the  ear  and  no  longer  is  able  to 
function  normally. 

usually  is  encased  in  a  film  of  moisture.  Both  dew  and  rain,  as  well 
as  pollen  and  dust,  are  retained  in  the  cavities  surrounding  the  shank. 
Thus  fungus  spores  lodging  near  the  base  or  middle  of  the  shank 
have  an  environment  very  favora'ble  for  germination  and  growth. 
This  fungus  growth  not  infrequently  may  start  on  the  outside  of  the 
shank,  invade  its  tissues,  and  cause  local  infections.  The  extent  of  in- 
fection depends  on  several  factors,  chief  of  which  are  the  nature  of 
the  fungi  and  the  resistance  of  the  plants  attached. 

If  the  shank  is  weakened  in  any  way,  either  by  mechanical  in- 
juries or  by  physiologic  disturbances  in  the  plant,  it  usually  is  more 
readily  invaded  by  fungi.  When  weakened  by  local  rotting,  the  shank 
often  breaks  or  crumples  under  the  weight  of  the  ear  (Fig.  58)  and 


1924] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


371 


FIG.  59. — THREE  SHANK  ATTACHMENTS 
Above,  bright  healthy  condition ;  center, 
dark  vascular  bundles  associated  with  Cep- 
halosporium ;  below,  a  shredded  condition 
indicating  that  the  ear  came  from  a  rotted 
and  prematurely  dead  shank. 


no  longer  is  able  to  function 
normally.  Such  injuries  fre- 
quently are  the  cause  of  light, 
chaffy  ears  that  would  not  be 
considered  for  seed.  But 
where  the  injuries  occur  late 
in  the  development  of  the  ear, 
the  reduction  in  quality  of 
grain  may  not  be  so  appar- 
ent. If  the  infecting  organ- 
ism *is  Diplodia  zeae,  the 
shank  and  the  butt  of  the  ear 
may  be  badly  rotted. 

Ears  selected  from  plants 
with  rotted  or  partially  rotted 
shanks  have  a  more  or  less 
discolored  or  shredded  shank 
attachment  (Fig.  59  and 
Plate  IV).  The  kernels  on 
ears  with  such  shank  attach- 
ments may  or  may  not  actu- 
ally be  infected.  Judged  on 
the  basis  of  viability,  vigor, 
and  freedom  from  infection, 
as  shown  in  this  study,  the 
percentage  of  desirable  seed 
ears  with  badly  discolored  or 
shredded  shank  is  compara- 
tively low  (Tables 46  and  51). 
Altho  some  badly  diseased 
ears  were  found  with  bright 
shank  attachments,  the  per- 
centage of  such  ears  also  was 
low  (Tables  44,  45,  46,  47, 
and  49,  and  Chart  22).  The 
data  from  these  experiments 
indicate  that  good  seed  ears 
have  bright,  clean  shanks  or 
shanks  with  only  slight  dis- 
colorations  (Plate  IV). 

EAR-TIP    COVERING 

Ears  whose  tips  are  ex- 
posed to  the  weather  before 
maturity  (Fig.  60)  often  are 


PLATE  IV 

A         A  clean,  sound  shank  is  an  important  consideration  in  the  selection  of 
good  seed  corn. 

B  Slightly  pink  shank. 

C  Pink  shank 

D  Brown  shank 

E  Shredded  shank 

F  Moldy  shank 

Good  seed  ears  have  bright  clean  shanks  or  shanks  with  only  slight  dis- 
coloration. 

1  Horny  seed 

2  Moderately  horny  seed 

.°>         Moderately  starchy  seed 
4         Starchy  seed 

Disease  resistance  has  been  found  to  be  rather  generally  associated  with 
seed  from  apparently  healthy  plants  that  is  nearly  disease-free,  horny, 
and  shows  vigorous  germination. 


372 


Corn  Root,  Stalk,  and  Ear  Rot  Diseases 


Plate  IV 


Illinois  Agricultural  Experiment  Station 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES  373 

infected  with  Fusarium  spp.  and  Diplodia  zeae.  Such  local  infections 
vary  in  extent  from  a  few  kernels  to  the  whole  ear.  Classifications 
made  in  these  studies  showed  that  the  tips  of  a  large  proportion  of 
the  infected  and  diseased  ears  had  been  exposed  (Tables  44,  45,  46, 
47,  and  49,  and  Chart  22).  Both  data  from  experiments  on  the 
physical  characters  of  seed  ears  and  general  experience  of  corn  breed- 
ers indicate  that  it  is  highly  desirable,  from  the  standpoint  of  free- 
dom from  infection,  that  the  tips  of  ears  should  be  well  covered  by 
the  husks  as  a  protection  from  the  weather  and  fungus  infection. 


KERNEL  INDENTATION 

For  many  years  the  indentation  of  the  corn  kernel  has  been  the 
subject  of  much  discussion,  controversy,  and  experimentation.  Experi- 
ments relating  to  this  specific  character  are  reviewed  elsewhere  in  this 
bulletin.  From  the  standpoint  of  best  yields  and  quality,  the  evidence 
of  much  experimentation  favors  long,  smoothly  dented  ears,  with  large 
well-developed  kernels  of  medium  depth.  It  has  been  found  in  these 
investigations,  covering  a  period  of  years,  that  careful  testing  for 
viability,  vigor,  and  freedom  from  disease  has  almost  invariably  re- 
sulted in  the  selection  of  corn  of  medium  smooth  to  smooth  indentation, 
regardless  of  source  and  previous  breeding.  Such  a  statement  does 
not  imply  that  ears  of  smooth  indentation  have  always  been  free  from 
infection  or  even  relatively  disease-free.  Some  smooth  corn  is  badly 
diseased  and  decidedly  inferior  in  quality. 

Comparatively  few  ears  of  rough  indentation  have  been  found  to 
pass  repeated  germination  tests  that  considered  vigor  and  freedom 
from  disease.  Rough  ears  that  have  passed  such  tests  at  this  Station 
have  proved  to  be  rather  susceptible  to  ear  rots  in  the  field.  They  also 
have  shown  no  superiority  in  yielding  ability  to  the  ears  more  smoothly 
dented.  Data  presented  in  Tables  44,  45,  46,  47,  and  49,  and  Chart  22 
show  that  95  to  100  percent  of  the  disease-free  seed  ears  were  mid- 
smooth  to  smooth  in  indentation.  These  data  are  supported  also  by 
many  data  and  much  experience  of  the  authors  not  herein  reported, 
and  by  the  experience  of  many  other  workers  thruout  Illinois. 


NATURE  OF  ENDOSPERM 

Kernel  structure  and  composition,  as  determined  physically  by  the 
quantity  of  vitreous,  or  horny,  endosperm  (Plate  IV),  is  closely 
correlated  with  kernel  indentation  in  most  commercial  varieties  of 


374 


BULLETIN   No.    255 


[August, 


dent  corn  in  the  corn  belt.  Altho  there  are  smooth  ears  that  are 
starchy,  and  rough  ears  that  are  horny,  this  seems  to  be  the  exception 
rather  than  the  rule.  In  general,  roughly  dented  kernels  are  de- 
cidedly more  starchy  and  lighter  in  specific  gravity  than  those  more 
smoothly  dented. 


FIG.  GO. — COVERED  AND  EXPOSED  EAR-TIPS 

Ears  whose  tips  are  exposed  to  the  weather  before  maturity  often  are  in- 
fected with  Fusarwm  spp.  and  Diplodia  zcae. 

Very  early  in  the  investigations  reported  in  this  bulletin  dif- 
ferences in  kernel  structure  of  diseased  and  of  relatively  disease-free 
ears  were  observed  and  recorded.  In  this  particular  study  ears  show- 
ing infection  with  Fusarium  moniliforme  and  Diplodia  zeae  and  those 
affected  with  scutellum  rot  were  found  to  be  much  more  starchy  than 
those  free  from  infection  (Tables  47  and  49).  Seed  which  tested 
nearly  disease-free  wras  found  repeatedly  to  contain  only  a  very  low 
percentage  of  ears  with  decidedly  starchy  kernels  (Tables  47  and  49). 
Trost  and  Hoffer100  and  Trost107  also  have  reported  this  condition. 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


375 


i  county 

Nearly 
disease-free 
(10  ears) 

1 

000 
O5  i-H 

000 

000 

000 

1-1  CD  CO 

000 

ooo 

t>-  CM  ^H 

03 

I 

w 

§ 

11 

.50 

I 

000 
CM  CO  >O 

§83 

000 

i-H 

000 

000 
CO  CM  iO 

000 

nd  county 

Nearly 
disease-free 
(10  ears) 

"8 

i 

s, 

ooo 

00  CM 

000 
t^  CO 

ooo 

ooo 

ooo 

000 

-23 

n 

J4 

o 
O 
« 

Diseased 
(10  ears) 

i 

OOO 
CM  GO 

ooo 

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Intermediate 
Starchy  

376 


BULLETIN   No.   255 


[August, 


LUSTER  OF  KERNEL 

Brightness,  or  luster,  of  the  germ  side  of  shelled  corn  is  a  physical 
character  that  has  long  been  used  by  veteran  corn  growers  in  selecting 

TABLE  45. — CERTAIN  PHYSICAL  CHARACTERISTICS  OF  EARS  WHICH  CLASSIFIED 
ON  THE  GERMINATOR  AS  DISEASED  AND  NEARLY  DISEASE-FREE 

Yellow  dent  ears  from  different  sources,  1922.     Classification  based  on  three  and 
sometimes  four  germination  tests  of  ten  kernels  each 


Characters  observed 

De  Witt  county 

Knox  county 

Tazewell  county 

Diseased 

(37  ears) 

Nearly 
disease- 
free 
(17  ears) 

Diseased 

(7  ears) 

Nearly 
disease- 
free 

(9  ears) 

Diseased 

(15  ears) 

Nearly 
disease- 
free 
(10  ears) 

Luster  of  ear 
Bright  

perct. 

0.0 
51.4 

48.6 

2.7 

24.3 
73.0 

18.9 
56.8 
24.3 

35.1 

27.1 
37.8 

0.0 
67.6 
32.4 

35.1 
40.6 
24.3 

perct. 

11.8 

82.4 
5.8 

5.8 

64.8 
29.4 

64.8 
35.2 
0.0 

100.0 
0.0 
0.0 

100.0 
0.0 
0.0 

88.2 
11.8 
0.0 

perct. 

0.0 
28.6 
71.4 

0.0 

85.7 
14.3 

0.0 
85.7 
14.3 

71.4 
0.0 
28.6 

100.0 
0.0 
0.0 

0.0 
100.0 
0.0 

perct. 

22.2 
66.7 
11.  '1 

0.0 

88.9 
11.1 

22.2 
66.7 
11.1 

66.7 
33.3 
0.0 

100.0 
0.0 
0.0 

88.9 
11.1 
0.0 

perct. 

0.0 
73.4 
26.6 

0.0 

20.0 
80.0 

0.0 
60.0 
40.0 

13.3 
40.0 
46.7 

93.3 
6.7 
0.0 

13.3 
60.0 
26.7 

perct. 

0.0 
100.0 
0.0 

0.0 

70.0 
30.0 

30.0 
50.0 
20.0 

100.0 
0.0 
0.0 

100.0 
0.0 
0.0 

90.0 
10.0 
0.0 

Intermediate              .  . 

Dull       

Shank  attachment 
Bright  

Slightly  pink  or  slightly 
brown        

Pink  or  brown  
Tip  of  ear 
Covered  by  husk    

Slightly  exposed 

Exposed     

Indentation 
Smooth  

Intermediate 

Rough  

Luster  of  kernel 
Bright  

Intermediate             .... 

Dull  

Kernel  composition 
Horny            

Intermediate.           .... 

Starchy  

seed.  These  studies  showed  that  altho  some  badly  infected  ears  may 
have  bright  kernels,  nearly  disease-free  seed  very  seldom  contains 
dull  kernels  (Tables  44,  45,  46,  47,  and  49). 


GENERAL  DISCUSSION 

Perhaps  the  most  consistent  differences  in  physical  characteristics 
between  the  Fusarium-infected  composites  and  the  good-seed  com- 
posites were  in  brightness  of  luster,  character  of  shank  attachment, 
and  evidence  of  ear-tip  exposure.  Among  the  Fusarium-infected  com- 
posites used  in  1921  and  1922  (Table  49),  only  a  small  percentage 
of  ears  could  be  classed  as  bright  in  luster — 9.7  and  12.4  percent,  re- 
spectively, in  the  two  years,  as  compared  with  53.4  and  62.0  percent 


1924] 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


377 


in  the  good  seed.  The  percentages  of  ears  with  bright,  sound  shank 
attachments  were  very  low — 3.12  and  1.0  percent,  as  compared  with 
87.2  and  30.7  percent  in  the  good  seed.  Also,  the  high  proportion  of 
ears  with  pink  or  brown  shanks — 67.8  and  71.1  percent  in  the  Fusarium- 
infected  composites  as  compared  with  2.3  and  28.2  in  the  good-seed 
composites — is  significant.  The  difference  in  percentage  of  ears  with 
covered  tips  in  1922,  12.3  percent  in  the  Fusarium-infected  com- 

TABLE  46. — CERTAIN  PHYSICAL  CHARACTERISTICS  OP  COMPOSITES  OF  MODERATELY 

DISEASED  AND  NEARLY  DISEASE-FREE  YELLOW  DENT  SEED  EARS, 

BLOOMINGTON,  1922 


Characters  observed 


Moderately 

diseased 
(1346  ears) 


Nearly 
disease-free 
(1103  ears) 


perct. 

Luster 

Bright 9.5 

Intermediate 51.3 

Dull 39.2 

Shank  attachment 

Bright 6.1 

Slightly  pink  or  slightly  brown 32 . 5 

Pink  or  brown '. 61 . 4 

Tip  of  ear 

Covered  with  husk 20.3 

Slightly  exposed 35 . 2 

Exposed 44 . 5 

Indentation 

Smooth 29 . 8 

Intermediate 33 . 5 

Rough 36. 7 

Brightness  of  kernel 

Bright 55.7 

Intermediate 26 . 1 

Dull 18.2 

Kernel  composition 

Horny 26 . 9 

Intermediate 43  0 

Starchy 30.1 


perct. 

53.4 

44.2 

2.4 

53.9 
38.9 

7.2 

57.2 
32.2 
10.6 

70.9 

24.1 

5.0 

89.9 
3.7 
6.4 

66.5 

32.6 

0.9 


posite  as  compared  with  71.8  percent  in  the  good-seed  composite,  sug- 
gests that  in  many  cases  the  initial  infections  of  Fusarium  moniliforme 
may  have  been  in  the  exposed  tips  of  the  ears,  from  which  point  of 
attack  the  fungus  spread  thruout  the  ear. 

Differences  between  the  Fusarium-infected  composites  and  good- 
seed  composites  in  indentation,  nature  of  endosperm,  and  kernel  luster 
are  not  so  consistent  as  differences  in  luster  of  ear,  character  of  shank 
attachment,  and  evidence  of  ear-tip  exposure.  This  may  be  accounted 
for  in  part  by  the  fact  that  the  Fusarium-infected  ears  that  also  were 
infected  with  Diplodia  zeae  and  those  affected  with  scutellum  rot  were 
not  included  in  the  seed  lots  infected  primarily  with  Fusarium 
moniliforme.  In  general  it  has  been  found  that  Fusarium-infected 
ears  are  usually  rougher  in  indentation  and  more  starchy  in  composi- 


PLATE  V 
A,  B,  C    Cob  interiors  of  good  seed  ears. 

In  the  coloring  of  the  interior  cob,  considerable  natural  variation  oc- 
curs. In  some  ears  the  coloration  extends  to  th?  point  of  attachment 
between  cob  and  shank,  and  thus  gives  the  shank  attachment  a  pink  or 
brown  appearance.  In  such  cases  pink  or  brown  shanks  are  normal. 

D,  E,  F   Cob  interiors  of  undesirable  seed  ears. 

Note  that  discolorations  at  the  butts  of  cobs  are  due  to  rotting  of  the 
tissues. 

Where  shank  discolorations  and  shreddings  are  plainly  the  result  of  de- 
cayed tissue,  the  seed  value  of  such  ears  is  very  questionable,  especially 
when  considered  from  the  standpoint  of  disease  resistance. 

G  Ear  of  corn  from  highly  resistant  strain  that  had  been  injured  by 
earworms. 

H  Ear  of  corn  from  susceptible  strain  that  had  been  injured  by  earworms. 
There  are  open-pollinated  strains  that  are  highly  resistant  to  certain  of 
the  corn  rot  diseases.  This  resistance  can  be  maintained  by  constant 
selection. 


378 


Corn  Root,  Stalk,  and  Ear  Rot  Diseases 


Plate  V 


Illinois  Agricultural  Experiment  Station 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


379 


tion.     Kernel  brightness  does  not  seem  to  be  any  evidence  of  nonin- 
fection  with  Fusarium  spp. 

Diplodia-infected  ears    (Table  49)   usually  lack  the  bright,  rich 
luster  and  clean  shank  attachments  characteristic  of  disease-free  ears, 


eo 


f* 

$  /O 


60 

50 
40 
JO 
20 
10 


BID      BSIPP      C  s£  E     SIR      BID     HIS 
Luster      Shank        Tip     Indentation   Kernel  Composition 

Moderately  Diseased 


yu 

eo 

\60 

i- 

r 

B  20 
I 

CL  10 

0 

yu 

70 

60 
SO 

30 
20 
/O 
0 

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• 

•  1 

. 

BID       BSP  P      C*£  E      S  /  ft     BID      H  /  S 
Luster       Shank          Tip     Indentation  Kernel  Composition 

Nearly  Disease-Free 

CHART  22. — PHYSICAL  CHARACTERISTICS  OF  MODERATELY  DISEASED  AND 
NEARLY  DISEASE-FREE  SEED  (For  meaning  of  letters,  see  Table  46) 
Good  seed  composites,  as  compared  with  diseased  seed  composites,  have 

been  found  to  contain  a  much  higher  percentage  of  ears  with  bright  luster, 

clean  shank  attachments,  covered  tips,  smooth  indentation,  bright  kernels, 

and  ears  horny  in  kernel  composition. 


380 


BULLETIN   No.   255 


TABLE  47. — CERTAIN  PHYSICAL  CHARACTERISTICS  OF  THE  SEED  EARS  ENTERING 
INTO  THE  NEARLY  DISEASE-FREE  COMPOSITES  AND  THE  COMPOSITES  AF- 
FECTED PRIMARILY  WITH  SCUTELLUM  ROT  IN  1920,  1921,  AND  1922 


19 

20 

19 

21 

19 

22 

Characters  observed 

Diseased 
(99  ears) 

Nearly 
disease- 
free 

(62  ears) 

Diseased 
(238  ears) 

Nearly 
disease- 
free 
(120  ears) 

Diseased 

(64  ears) 

Nearly 
disease- 
free 

(202  ears) 

Luster 
Bright            

perct. 
8  0 

perct. 
75  8 

perct. 
10  9 

perct. 
53  4 

perct. 
4  7 

perct. 
62  0 

Intermediate         .... 

30  3 

24  2 

67  2 

45  1 

40  7 

34  6 

Dull  

61  7 

0  0 

21  9 

1.5 

54.6 

3.4 

Shank  attachment 
Bright          

10  1 

87  0 

2  5 

87.2 

23.4 

30.7 

Slightly  pink  or  slightly 
brown  

40.4 

11.4 

49.2 

10.5 

23.4 

41.1 

Pink  or  brown  

49  5 

1.6 

48  3 

2.3 

53.2 

28.2 

Tip  of  ear 
Covered  by  husk  

40  4 

72  6 

24  8 

71,4 

29.7 

71.8 

Slightly  exposed  

28  3 

21  0 

35  7 

26  3 

34  4 

18  3 

Exposed  

31  3 

6.4 

39.5 

2.3 

35.9 

9.9 

Indentation 
Smooth  

17  1 

71  0 

14  3 

75.9 

18.8 

68.9 

Intermediate     

46  5 

29  0 

33  6 

21  8 

40  6 

26.7 

Rough  

36  4 

0.0 

52.1 

2.3 

40.6 

4.4 

Brightness  of  kernel 
Bright 

59  5 

100  0 

42  4 

98  5 

70  3 

97  0 

Intermediate     

18  2 

0  0 

35  3 

1.5 

15.6 

2.5 

Dull 

22  3 

0  0 

22  3 

0  0 

14.1 

0.5 

Kernel  composition 
Horny.           

1  0 

17.8 

15.5 

74.4 

18.7 

87.7 

Intermediate    '.  

35  4 

80.6 

59  3 

24.8 

46.9 

12.3 

Starchy  

63.6 

1.6 

25.2 

0.8 

34.4 

0.0 

TABLE  48. — GERMINATION  RECORDS  OF  SEED  EARS  ENTERING  INTO  THE  SCUTELLUM 
ROT  AND  THE  NEARLY  DISEASE-FREE  COMPOSITES  IN  1920,  1921,  AND  1922 

Percentages  are  based  on  3  ten-kernel  tests  from  each  ear.     Ears  are  described 
in  Table  47 


19 

20 

19 

21 

19 

22 

Characters  observed 

Diseased 
(99  ears) 

Nearly 
disease- 
free 
(62  ears) 

Diseased 
(238  ears) 

Nearly 
disease- 
free 
(120ears) 

Diseased 
(64  ears) 

Nearly 
disease- 
free 
(202  ears) 

Viability  

perct. 
99.9 

perct. 
100.0 

perct. 
99.7 

perct. 
100.0 

perct. 
99.5 

perct. 
100.0 

Seedlings  showing  scutel- 
lum  rot  when  sectioned  . 
Seedlings  showing  visible 
infection  with  Fusarium 
moniliforme  

26.4 
trace 

1.3 
0.0 

50.6 
3.5 

3.5 
0.0 

57.0 
2  2 

4.6 
0  0 

Seedlings  showing  visible 
infection  with  Diplodia 
zeae  

trace 

0.0 

0.0 

0.0 

0.0 

0.0 

19X4] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


381 


TABLE  49. — CERTAIN  PHYSICAL  CHARACTERISTICS  OP  SEED  EARS  ENTERING  INTO 
COMPOSITES  INFECTED  PRIMARILY  WITH  FUSARIUM  AND  DIPLODIA, 
AND   THE    NEARLY   DISEASE-FREE    SEED   COMPOSITES   OP 
YELLOW  DENT  CORN  IN  1921  AND  1922 


Characters  observed 

1921 

1922 

Fusarium 
(31  ears) 

Diplodia 

(51  ears) 

Nearly 
disease-, 
free 
(120  ears) 

?usarium 
(97  ears) 

Diplodia 
(191  ears) 

Nearly 
disease- 
free 
(202  ears) 

Luster 
Bright  

perct. 

9.7 
74.2 
16.1 

3.2 

29.0 

67.8 

perct. 

19.6 
62.7 
17.7 

2.0 

11.8 

86.2 

perct. 

53.4 
45.1 
1.5 

87.2 

10.5 
2.3 

71.4 
26.3 
2.3 

75.9 
21.8 
2.3 

98.5 
1.5 
0.0 

74.4 

24.8 
0.8 

perct. 

12.4 

75.2 
12.4 

1.0 

27.9 
71.1 

12.3 

77.4 
10.3 

75.2 
21.7 
3.1 

90.7 
7.2 
2.1 

76.3 
23.7 
0.0 

perct. 

31.9 

48.7 
19.4 

4.1 

18.9 
77.0 

71.8 
22.5 
5.7 

51.8 
26.7 
21.5 

60.8 
39.2 
0.0 

perct. 

62.0 
34.6 
3.4 

30.7 

41.1 

28.2 

71.8 
18.3 
9.9 

68.9 
26.7 
4.4 

97.0 
2.5 
0.5 

87.7 
12.3 
0.0 

Intermediate  

Dull  

Shank  attachment 
Bright  

Slightly  pink  or  slightly 
brown  

Pink  or  brown  

Tip  of  ear 
Covered  by  husk  

Slightly  exposed  

Exposed  

Indentation 
Smooth  

45.2 
48.3 
6.5 

58.1 
29.0 
12.9 

32  2 

25.8 
42.0 

72.5 
19.6 
7.9 

74.5 
15.7 
9.8 

66.6 
27.5 
5.9 

Intermediate  

Rough  

Kernel  brightness 
Bright  

Intermediate 

Dull  

Kernel  composition 
Horny  

Intermediate     

Starchy  

TABLE  50. — GERMINATION  RECORDS  OF  SEED  EARS  ENTERING  INTO  THE  COMPO 

SITES  INFECTED  PRIMARILY  WITH  FtrsARiuM  AND  DIPLODIA, 

AND  THE  NEARLY  DISEASE-FREE  COMPOSITES  OF 

YELLOW  DENT  CORN.  IN  1921  AND  1922 

Percentages  are  based  on  3  ten-kernel  tests  from  each  ear.      Ears  are  described 
in  Table  49 


1921 

1922 

Characters  observed 

Fusa- 
rium 

Diplodia 

Nearly 
disease- 
free 

Fusa- 
rium 

Diplodia 

Nearly 
disease- 
free 

Viability            

perct. 
97  2 

perct. 
91  5 

perct. 
100  0 

perct. 
97  5 

perct. 
87  0 

perct. 
100  0 

Seedlings  showing  scutel- 
lum  rot  when  sectioned  . 
Seedlings  showing  visible 
infection  with  Fusarium 
moniliforme  

0.0 
57  0 

0.0 
0  0 

3.5 
0  0 

4.0 
92  6 

3.0 
0  5 

4.6 
0.0 

Seedlings  showing  visible 
infection  with  Diplodia 
zeae  

0.0 

64.0 

0.0 

0.0 

92.6 

0.0 

382  BULLETIN   No.    255  [August, 

but  often  they  are  just  as  horny  in  kernel  composition  as  is  good  seed. 
When  infection  has  entered  the  ear  thru  the  shank,  the  kernels  are 
somewhat  more  starchy  than  are  kernels  on  uninfected  ears.  In  gen- 
eral, however,  the  selection  of  horny  seed  is  no  assurance  against  ears 
infected  with  Diplodia  zeae.  Frequently,  infected  ears  that  might  be 
selected  for  seed  contain  a  few  kernels  that  have  been  completely  over- 
run by  the  fungus  and  present  a  brown  appearance  on  the  germ  side 
of  the  kernel.  Ears  containing  such  discolored  kernels  should  not  be 
considered  for  seed  as  they  very  likely  contain  many  kernels  of  good 
appearance  that  are  slightly  infected  with  Diplodia  zeae. 

VALUE  OF  SINGLE  EAR  CHARACTERS  IN  SEED  SELECTION 

From  the  previous  data  it  is  evident  that  there  are  distinct  dif- 
ferences in  the  general  appearance  of  nearly  disease-free  seed  ears 
and  diseased  seed  ears.  These  differences  in  physical  characteristics 
may  not  always  be  confined  to  a  single  ear  chara'cter,  such  as  luster 
of  ear,  nature  of  shank  attachment,  character  of  endosperm,  or  kernel 
indentation.  On  this  account  there  is  much  advantage  in  consider- 
ing a  number  of  characters  in  the  physical  selection  of  seed  ears. 
However,  certain  single  ear  characters,  perhaps  on  account  of  their 
conspicuousness,  have  received  undue  emphasis  as  criterions  of  field 
performance.  Data  on  the  value  of  considering  single  ear  characters 
in  seed  selection  are  given  in  Tables  51  to  60. 

SHANK  ATTACHMENT 

Badly  discolored  and  shredded  shank  attachments  very  frequently 
are  associated  with  poor  seed  condition.  The  data  thus  far  collected, 
however,  do  not  show  that  variations  in  discolorations  or  shredding  are 
significant.  Practically  the  same  high  percentages  of  ears  with  brown 
shank  attachments  were  found  in  both  Fusarium  and  Diplodia  com- 
posites (Table  51).  Also,  ears  with  shredded  attachments  were  ob- 
served in  both  Fusarium  and  scutellum  rot  composites. 

Data  bearing  on  the  relation  of  character  of  shank  attachments  to 
yield  are  presented  in  Tables  52  and  53.  Mr.  R.  I.  McKeighan's  strain 
of  yellow  dent  corn  was  used  in  the  experiment  reported  in  Table  52. 
The  corn  had  not  been  selected  from  special  plants  in  the  field,  nor  had 
a  germination  test  been  made  of  the  ears  prior  to  the  selection  and 
grouping  for  planting.  Results  reported  in  Table  52  are  decidedly  in 
favor  of  ears  with  sound,  bright  shanks. 

The  reduction  in  acre  yield  (Table  52)  of  8.8  bushels,  or  12.9  per- 
cent, in  plots  planted  with  seed  from  ears  with  shanks  showing  black 
bundles  is  of  special  interest.  In  this  case,  they  were  ears  with  shank 
attachments  having  many  black  or  brown  vascular  bundles  set  in  clear 
white  pith  (Fig.  59).  Reddy  and  Holbert81  have  shown  that  this 


1924} 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


383 


TABLE  51. — DETAILED  DESCRIPTION  OP  SHANK  ATTACHMENTS  OF  THE  SEED  EARS 
ENTERING  INTO  THE  STANDARD  COMPOSITES  PLANTED  IN  1922 


Character  of  shank  attachment 

Fusarium- 
infected 
composite 
(97  ears) 

Diplodia- 
infected 
composite 
(191  ears) 

Scutellum 
rotted 
composite 
(64  ears) 

Nearly  dis- 
ease-free 
composite 

(202  ears) 

Bright       

perct. 
1  0 

perct. 
.  3  1 

perct. 
23  4 

perct. 
30  7 

Bright  but  slightly  shredded.  .  . 

0.0 

1.0 

0.0 

0.0 

Total  bright  

1.0 

4.1 

23.4 

30.7 

Medium           

0  0 

0  0 

3  1 

6  4 

Slightly  brown  

21.7 

15  2 

11  0 

25.7 

Slightly  pink  

1  0 

1  6 

9  4 

5  0 

Slightly  brown  and  slightly  shred- 
ded   

5  2 

2  1 

0  0 

4  0 

Total  medium  

27.9 

18.9 

23.5 

41.1 

Dull  

0  0 

0  0 

3  1 

6  9 

Brown  

46  4 

45  6 

23  4 

11  4 

Pink  

3  1 

1  6 

17  2 

1  0 

Red  

9  3 

6  8 

0  0 

3  0 

Brown  and  shredded  

11  3 

22  0 

9  4 

5  9 

Red  and  shredded  

1  0 

1  0 

0  0 

0  0 

Total  dull  .  . 

71.1 

77.0 

53  .  1 

28.2 

blackening  of  the  vascular  bundles  very  frequently  is  caused  by  in- 
fection with  Cephalosporium  acremonium.  No  doubt  a  high  per- 
centage of  the  kernels,  as  well  as  of  the  shanks  of  these  ears,  were  in- 
fected with  this  organism,  which  probably  was  responsible  for  the  re- 
duction in  yield  in  this  particular  case.  Cephalosporium  infection  of 
kernels  thru  the  shank,  however,  does  not  always  discolor  the  vascular 
system  enough  to  make  such  discolorations  plainly  visible.  Neither 
does  the  presence  of  black  bundles  in  the  shank  attachment  neces- 
sarily indicate  kernel  infection  with  this  organism.  Under  certain 

TABLE  52. — RELATION  OF  CONDITION  OF  SHANK  ATTACHMENT  TO  YIELD 

Yellow  dent  corn  grown  on  brown  silt  loam  of  good  fertility,  on  which  corn  had 
been  grown  the  previous  season,  near  Yates  City,  1921 


Condition  of  shank  attachment 

Total  acre 
yield 

Reduction  in  yield 

Bright  (check)  

bu. 
68.4 
61.2 

72.2 
60.9 

72.2 
61.7 

68.2 
59.4 

bu. 

7.2 

11.3 
10.5 

8.8 

perct. 
10.5 

15.7 
14.5 
12.9 

Shredded  

Bright  (check)  

Pink  

Bright  (check)  

Brown  

Bright  (check)  

Black-bundle  

384 


BULLETIN   No.   255 


[August, 


conditions  corn  grown  from  seed  infected  with  Cephalosporium  may 
yield  just  as  much  as  corn  grown  from  uninfected  seed ;  under  other 
conditions  the  same  seed  may  produce  a  crop  very  inferior  in  both 
quantity  and  quality  (Table  40). 

In  the  experiment  reported  in  Table  53  the  reduction  in  the  plots 
planted  with  corn  from  ears  showing  the  presence  of  black  bundles  in 
the  shank  was  only  2.5  bushels  per  acre,  or  3.9  percent.  The  factors 
determining  reductions  in  yield  due  to  seed  infection  with  Cephalos- 
porium are  not  yet  clearly  understood.  This  phase  of  the  corn  disease 
situation  is  being  investigated  further.  More  data  and  further  dis- 
cussion are  presented  by  Reddy  and  Holbert.81 

Ears  included  in  the  experiment  reported  in  Table  53  had  been 
selected  in  the  field  from  good  standing  plants,  and  were  classed  as 
nearly  disease-free  in  the  first  germination  test.  A  second  and  third 
germination  test  indicated  that  the  ears  with  shredded  shank  attach- 
ments were  slightly  infected  with  Diplodia  zeae.  Plots  planted  with 
these  ears  were  the  only  series  in  this  experiment  to  show  an  ap- 
preciable reduction  in  yield. 

There  is  much  variation  in  color  and  in  intensity  of  color  of  cob 
interiors  either  when  viewed  in  cross-section  after  the  cobs  have  been 
broken  or  when  viewed  in  longitudinal  section  after  they  have  been 
sawed  longitudinally  (Plate  V).  Interior  cob  coloring  variations  pre- 
vail in  most  open-pollinated  strains  of  corn,  even  in  those  that  have 
been  selected  rather  closely  for  several  years.  It  seems  probable  in 
many  cases  that  red,  pink,  and  brown  colorings  in  the  shank  are  due 
simply  to  lodgment  in  the  shank  attachment  of  the  same  pigment  found 
in  the  vascular  cylinder  of  the  cob  and  do  not  indicate  infection. 
Hence,  in  observing  the  nature  of  the  shank  attachment  for  the  selec- 

TABLE  53. — RELATION  OF  CONDITION  OF  SHANK  ATTACHMENT  TO  YIELD 
Yellow  dent  corn  grown  on  University  South  Farm,  Urbana,  1921 


Condition  of  shank  attachment 

Total  acre 
yield 

Reductio 

n  in  yield 

Bright  (check)         

bu. 
67  8 

bu. 

perct. 

Shredded  

53  6 

14.2 

20  9 

Bright  (check)         .    . 

65  0 

Pink  .  .  . 

62  5 

2  5 

3  8 

Bright  (check)                 .    . 

63  8 

Brown 

65  2 

-1  4 

-2  2 

Bright  (check)  

64  0 

Red  

66  9 

-2.9 

-4.5 

Bright  (check)  

63  6 

Black-bundle  

61.1 

2.5 

3.9 

1924} 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


385 


TABLE  54.— PERCENTAGE  OF  DIFFERENTLY  COLORED  VASCULAR  CYLINDERS  OF  COBS 
FROM  THE  GOOD-SEED,  FUSARIUM-!NFECTED,  AND  DIPLODIA-!NFECTED 
COMPOSITES  SELECTED  FOR  PLANTING  IN  1923 


Condition  of  shank 
attachment 

Relative  amount  of 
pigmentation  and 
coloration  in  the 
vascular  cylinder  in 
the  interior  of  cob 

Seed  composites 

Nearly  dis- 
ease-free 
(324  ears) 

Fusarium- 
infected 

(145  ears) 

Diplodia- 
infected 
(280  ears) 

Bright   

(None  .           

perct. 
34.6 
36.7 
24.4 

0.9 
1.9 
12 

0.0 
0.0 
0.3 

0.0 
0.0 
0.0 

perct. 
6.9 
6.9 
11.0 

4.8 
15.9 
22.1 

3.5 
8.2 
13.8 

0.7 
2.1 
4.1 

perct. 
2.9 
7.8 
2.9 

2.9 
12.9 
16.0 

0.7 
15.0 
14.6 

1.8 
14.6 
7.9 

\  Slight  to  moderate  .  .  . 
[Considerable 

Slightly  pink  or  slightly 
brown  

(None. 

I  Slight  to  moderated  .  . 
[Considerable  

Pink  or  brown  

(None  

j  Slight  to  moderate  .  . 
[Considerable 

Shredded  

(None  

•j  Slight  to  moderate.  .  . 
[Considerable  

tion  of  seed,  it  is  very  important  to  distinguish  between  normal  colora- 
tions and  discolorations  resulting  from  decayed  tissues. 

During  the  spring  of  1923  a  study  was  made  of  the  color  of  the 
vascular  cylinder  of  cobs  taken  from  the  standard  composites.  Some 
of  these  data  are  reported  in  Tables  54,  55,  and  56.  In  the  nearly 
disease-free  composite  (Tables  54  and  55)  the  different  degrees  of 
coloration  in  the  vascular  cylinder  of  the  cobs  (Plate  V)  were  fairly 
evenly  divided,  there  being  35.5  percent  with  no  coloration,  38.6  per- 
cent with  a  slight  to  moderate  amount,  and  25.9  percent  with  a  con- 
siderable amount.  However,  in  both  the  Fusarium-infected  and 
Diplodia-inf ected  composites  much  larger  proportions  of  the  cobs  had 
colored  vascular  cylinders.  Only  8.3  percent  of  the  Diplodia-infected 
ears,  as  compared  with  35.5  percent  in  the  nearly  disease-free  ears, 
had  cobs  showing  no  coloration  of  the  vascular  cylinders. 

The  proportion  of  ears  having  broken  at  the  final  shank  node,  or 
the  node  nearest  the  ear,  was  very  much  less  in  the  nearly  disease-free 

TABLE  55. — SUMMARY  OF  DATA  PRESENTED  IN  TABLE  54 


Relative  amount  of  pigmentation  and 
coloration  in  the  vascular  cylinder 
in  the  interior  of  the  cob 

Seed  composites 

Nearly 
disease-free 
(324  ears) 

Fusarium- 
infected 
(145  ears) 

Diplodia- 
infected 
(280  ears) 

None  

perct. 
35.5 
38.6 
25.9 

perct. 
15.9 
33.1 
51.0 

perct. 
8.3 
50.3 
41.4 

Slight  to  moderate  

Considerable  

386 


BULLETIN    No.    255 


[August, 


TABLE  56.— DATA  ON  PLACE  OP  BREAKING  PROM  SHANK  OF  EARS  COM- 
PRIZING THE  STANDARD  COMPOSITES  FOR  PLANTING  IN  1923 


Place  at  which  ear  was  broken 
from  shank 

Seed  composites 

Nearly 
disease-free 
(324  ears) 

Fusarium- 
infected 

(145  ears) 

Diplodia 
infected 
(280  ears) 

At  final  shank  node  

pcrct. 
29.6 
70.4 

perct. 
71.7 

28.3 

perct. 
70.7 
29.3 

Below  final  shank  node  .  . 

composite  than  in  either  of  the  other  composites  (Table  56),  29.6  per- 
cent in  the  good-seed  composite  as  compared  with  71.7  and  70.7  percent 
in  the  Fusarium-infected  and  the  Diplodia-infected  composites,  re- 
spectively. This  difference  in  the  place  at  which  the  ear  breaks  from 
the  shank  would  appear  to  be  significant.  Unfortunately  there  are 
only  one  year 's  data  on  this  point. 

Where  shank  discolorations  and  shreddings  are  plainly  the  result 
of  decayed  tissue,  the  seed  value  of  such  ears  is  very  questionable,  es- 
pecially when  considered  from  the  standpoint  of  disease  resistance. 
Data  presented  later  show  that  ears  with  rotted,  shredded,  and  badly 
discolored  shank  attachments  can  have  no  part  in  the  development  of 
strains  of  corn  more  nearly  resistant  to  the  rot  diseases. 

NATURE  OF  ENDOSPERM 

Differences  in  the  nature  of  endosperm  in  nearly  disease-free  and 
diseased  ears  of  seed  corn  were  observed  very  early  in  the  investiga- 
tions reported  in  this  bulletin.  Since  1917,  ears  with  horny  kernels 
and  ears  with  starchy  kernels  (Plate  IV)  have  been  compared  in  ex- 
periments to  study  the  behavior  under  different  conditions  of  corn 
grown  from  seed  differing  in  endosperm  character.  Yields  from  these 
experiments  are  presented  in  Table  57  and  Chart  23.  The  differences 
in  grain  yields  from  corn  grown  from  starchy  seed  and  that  grown 
from  horny  seed  varied  from  slight  increases  to  reductions  of  35 
bushels  per  acre,  or  28  percent,  depending  on  the  previous  cropping, 
fertility  of  soil,  time  of  planting,  and  other  factors. 

In  1919,  at  Bloomington,  the  plots  were  planted  with  horny  and 
starchy  kernels  selected  from  the  same  ears.  The  same  number  of 
both  horny  and  starchy  kernels  was  used  from  each  of  the  ears  enter- 
ing into  the  experiment.  The  selection  of  the  kernels  was  based  solely 
on  the  physical  appearance  of  the  endosperm.  The  difference  in  the 
resulting  yields,  in  favor  of  the  horny  kernels,  is  very  significant. 

The  starchy  seed  used  in  1920  and  in  1921  was  nearly  disease- 
free.  The  same  composites  of  horny  and  starchy  seed  were  used  in 
all  the  experiments  in  1921.  At  Urbana  where  corn  followed  clover 
the  difference  in  yield  in  favor  of  the  horny  seed  was  only  2.2  bushels 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


387 


per  acre,  or  3.1  percent,  but  where  corn  followed  corn  in  the  same 
rotation  series  the  difference  was  8.2  bushels,  or  12.7  percent,  in  favor 
of  the  horny  seed.  Plantings  of  starchy  and  horny  seed  were  made 
on  the  same  day.  Both  were  nearly  disease-free.  Such  results  sug- 
gest that  previous  cropping  may  be  a  very  important  factor  in  de- 
termining the  comparative  yields  of  corn  grown  from  horny  and  from 
starchy  seed  where  both  kinds  of  seed  are  nearly  disease-free. 

In  1922  the  same  nearly  disease-free  horny  and  starchy  composites 
and  also  diseased  starchy  composites  were  used  in  all  experiments. 
Where  the  previous  crop  had  been  corn,  the  reductions  in  yield,  where 
starchy  seed  was  used,  usually  were  sufficiently  large  to  be  significant 
even  tho  the  starchy  seed  was  nearly  disease-free. 

Further  data  on  the  relative  seed  value  of  infected  and  nearly 
disease-free  starchy  seed  are  given  in  Table  58  and  Chart  24.  The 
same  seed  composites  were  used  in  these  experiments  as  in  those  re- 
ported for  1922  in  Table  57.  None  of  these  experiments  was  located 
on  ground  that  had  produced  corn  the  previous  year.  In  the  experi- 
ment near  Grirard,  Macoupin  county,  the  difference  in  acre  yield  of 
sound  corn  between  the  nearly  disease-free  starchy  and  the  nearly 

Yields  from  Starchy  Seed  I  Increase  in  Yield  Due  to 

Time  of      Condition  of\  f^e  Use  of  Nearly  Disease- 
Place  Prer/ovs  Crop   Planting      Starchy  Seea\  ^ee  Horny  Seed 


B/oomington-StveetClwer-Ear/u-Relat/ve/y  Disease-Free 


Bloom/naton-Com  ftfrs.  from Virgin Sotf!  -  Ear/y  -  Near/y  D/seasf-free 


naton     /t/fa/fa  (2  frs.j      Early      Diseased 


B/oomington-SprinqWheat-MeJ/vm-Wear/uDaease-free 


Bloom  ing  ton-  Wmter  Wheat-Medium-Near/y  Disease 


Urbana  Corn  £ar/y  Hearty  D/sease-Fret 


Urbana  C/orer   Eor/y  /Vear/y  Disease  -free 


Virginia-  C/wer-  Lats  -  tJear/y  Disease-free 


Norma/  Wheat    Late    Diseased 


/92Z 


IOO      90     8O       7O      60      SO      4O       30      20        /O 


10       20      30       -fO 


CHART  23. — SUPERIORITY  OP  HORNY  SEED    (Table  57) 

Under  the  many  conditions  encountered  in  six  years'  experimentation,  corn 
grown  from  nearly  disease-free  horny  seed  consistently  yielded  more  than  corn 
grown  from  starchy  seed. 


388 


BULLETIN   No.   255 


[August, 


disease-free  horny  seed  lots,  3.3  bushels,  was  not  significant.  At 
Yates  City,  Knox  county,  the  difference  was  5.9  bushels,  which  is 
over  five  times  the  probable  error,  thus  being  significant.  At  Stan- 
ford, McLean  county,  the  yields  were  practically  the  same,  33.5  and 

TABLE  57. — YIELDS  FROM  HORNY  AND  FROM  STARCHY  SEED 

Yellow  dent  corn  grown  on  brown  silt  loam  at  various  points  in  Illinois, 

1917  to  1923 


Year 

Location  of 
experiment 

Previous 
crop 

Relative 
time  of 
planting 

Condition  of 
starchy  seed 

Acre  yield  from  — 

Reduction  in 
yield  from 
starchy  seed 

Horny 
(disease- 
free) 

Starchy 

1917 

Bloomington.  . 

Sweet  clover. 

Early  

Relatively 
disease-free 

bu. 
74.4 

bu. 
70.3 

bu. 

4.1 

pfrct. 
5.5 

1918 

Bloomington  .  . 
Bloomington.  . 

Winter  wheat 

Corn  (2d  yr. 
from  virgin 

Early  
Early  

Relatively 
disease  -free 
Nearly  dis- 
ease-free .  . 

68.2 
100.6 

54.7 
92.4 

13.5 
8.2 

19.8 
8.2 

1919 

Bloomington.  . 

Alfalfa 
(12  yrs.)  .  . 

Early  

Diseased.  .  .  . 

125.0 

90.0 

35.0 

28.0 

1920 

Bloomington.  . 
Bloomington.  . 

Spring  wheat 
Winter  wheat 

Intermediate 
Intermediate 

Nearly 
disease-free 
Nearly 
disease  -free 

75.3 
69.5 

70.5 
69.4 

4.8 
0.1 

6.4 
0.1 

1921 

Urbana  

Corn  

Early  

Nearly 
disease-free 
Nearly 
disease-free 
Nearly 
disease-free 
Diseased.  .  .  . 
Diseased.  .  .  . 

64.7 
72.1 

64.2 
72.8 
70.2 

56.5 
69.9 

55.6 

62.7 
68.2 

8.2 
2.2 

8.6 
10.1 
12.0 

12.7 
3.1 

13  4 
13.9 
17.1 

Urbana  

Clover  
Clover  

Early  
Late  

Virginia    

Wheat 

Late 

Normal  .       ... 

Wheat      .... 

Late. 

1922 

Girard  
Girard  
Bloomington  . 
Bloomington.  . 

Urbana  

Corn  
Corn  
Corn  

Early  
Early  
Late  

Nearly 
disease-free 
Diseased  .... 

Nearly 
disease  -free 
Nearly 
disease-free 

Nearly 
disease-free 

40.7 
46.2 

75.3 
96.3 

57.5 

38.5 
34.4 

67.8 
91.2 

45.5 

2.2 
11.8 

7.5 
5.1 

12.0 

5.4 
25.5 

10.0 
53 

20.9 

Corn  
Clover  

Late  
Intermediate 

1923 

Bloomington.  . 
Bloomington  . 

Bloomington.  . 
Bloomington.  . 

Bloomington.  . 
Bloomington.  . 

Hopedale  
Hopedale  

Alfalfa  
Alfalfa  

Corn  
Corn  

Corn  
Corn  

Corn  
Corn  

Early  
Late  

Early  
Late  

Early  
Late  

Intermediate 
Late  

Nearly 
disease  -free 
Nearly 
disease-free 

Nearly 
disease  -free 
Nearly 
disease-free 

Nearly 
disease-free 
Nearly 
disease-free 

Nearly 
disease-free 
Nearly 
disease  -free 

84.0 
96.4 

47.2 
46.7 

66.3 
79.7 

67.4 
78.7 

86.0 
85.6 

40.5 
41.9 

63.1 
74.4 

62.7 
68.1 

-2.0 
10.8 

6.7 
4.8 

3.2 
5.3 

4.7 
10.6 

-2.4 
11  2 

14.2 
10.3 

4.8 
6.6 

7.0 
3.5 

Mean  reduction  in  acre  yield  of  corn  in  plots  planted  to  starchy  seed,  7.9  +  .95 
bushels. 
.    7.9 

=8.32.     Odds  greater  than  one  million  to  one. 

.95 


WS4] 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


389 


34.0  bushels.  However,  the  corn  grown  from  the  infected  starchy  seed 
was  decidedly  inferior  in  yielding  ability  to  that  grown  from  the  good 
horny  seed  in  every  instance,  the  differences  in  yield  in  favor  of  the 
horny  seed  ranging  from  4  to  11.6  times  the  probable  error. 

Additional  data  on  the  behavior  of  the  nearly  disease-free  horny 
and  starchy  composites  in  experiments  made  at  Urbana  are  presented 
in  Table  59»  In  spite  of  the  fact  that  the  starchy  seed  was  nearly 
disease-free,  the  differences  in  yield  of  sound  corn  between  corn  grown 
from  such  seed  and  from  nearly  disease-free  horny  seed  ranged,  in  the 
experiments  where  corn  followed  corn,  from  2.4  bushels  per  acre,  or 
9.1  percent,  to  8.7 
bushels,  or  36.7  per- 
cent, differences  suffi- 
ciently large  to  be 
significant.  In  the 
plantings  following 
clover  such  differ- 
ences ranged  from  3.7 
bushels  per  acre,  or 
6.9  percent,  to  14.7 
bushels,  or  26.3  per- 
cent. 

The  data  from  ex- 
periments extending 
over  a  period  of  seven 
years  (Tables  57,  58, 
and  59) ,  together  with 
the  fact  that  the  large 
majority  of  starchy 
seed  in  seed  stocks  in 
the  corn  belt  are  likely 
to  be  more  or  less  dis- 
eased, justify  the  dis- 
carding of  starchy 
ears  for  seed  pur- 
poses. 


70 

60 
SO 

20 
/O 
0 

\ 

H     H   H1 

r  1  1     r  t  t     r  1  1 

1  1  £       ^44       144 

Girard                fores  City             Stanford 

70 


60 


50 


40 


30 


20 


/O 


LUSTER  OF  KERNEL 
Altho     most     ears 
with     discolored     or 


CHART   24. — YIELD  OF   SOUND  CORN  AS  AFFECTED  BY 
CHARACTER  OF   ENDOSPERM   AND  SEED   INFECTION 
(Table  58) 
The  corn  grown  from  the  infected  starchy  seed  was 


brown  kprnpl  tins  arp    (lecidedly  inferior  in  yielding  ability  to  that  grown  from 
town  Keinei      is  are  thc  good  horny  geed  in  cyorv  instance 

likely  to  be  infected, 

there  are  ears  of  horny  composition  with  kernels  decidedly  brown  on 

the  germ  side  that  show  no  evidence  of  being  infected  when  tested 


390 


BULLETIN   No.   255 


[August, 


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CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


391 


on  the  germinator  in  the  usual  way.  The  seed  value  of  such  ears 
was  the  subject  of  a  series  of  experiments  reported  in  Table  60  and 
Chart  25. 

At  Urbana  there  was  practically  no  difference  in  yields  in  the  plant- 
ings following  clover,  but  in  the  plantings  following  corn  in  the  same 
rotation  series,  planted  on  the  same  day,  there'  was  a  reduction  of  6.8 
bushels  per  acre,  or  10.1  percent.  In  each  of  the  experiments  at 
Bloomington  seed  from  different  sources  was  used.  In  four  out  of 
the  five  experiments,  corn  grown  from  brown-tipped  horny  seed 
yielded  less  than  corn  grown  from  bright-tipped  horny  seed. 

There  was  evidence  that  the  brown-tipped  kernels  on  some  of  the 
ears  used  in  the  above-described  experiments  may  have  been  infected 
with  an  organism,  and  that  the  infection  could  not  be  detected  readily 
either  on  or  in  the  germinating  seedling.  There  also  was  evidence  that 
brown-tipped  kernels,  at  least  in  some  ears  of  corn,  are  normal,  and 
that  this  characteristic  is  inherited.  However,  experimental  data  are 
decidedly  in  favor  of  the  selection  of  ears  whose  kernels  are  bright  in 
every  respect. 

An  analysis  of  all  the  data  presented  in  Tables  43  to  60,  inclusive, 
indicates  that  ears  infected  with  Fusarium,  Diplodia,  or  Cephalos- 
porium  and  ears  affected  with  scutellum  rot  very  frequently  have 
marked  physical  characteristics  by  which  they  can  be  detected  and 


CHART  25. — SUPERIORITY  OF  BRIGHT-TIPPED  KERNELS  OVER  BROWN-TIPPED 

FOR  SEED  (Table  60) 

Experimental  data  are  decidedly  in  favor  of  the  selection  of  ears 
having  kernels  with  bright  tips. 


392 


BULLETIN   No.   255 


[August, 


TABLE  59. — YIELDS  FROM  NEARLY  DISEASE-FREE  HORNY  SEED  AND 
PROM  NEARLY  DISEASE-FREE  STARCHY  SEED 

Yellow  dent  corn  grown  on  brown  silt  loam,  University  South  Farm,  Urbana.  1922 


Rotation 

Previous 
crop 

Character 
of 
Seed 

Acre  yield 

Reduction  in 
sound  corn  from 
starchy  seed 

Total 

Sound 

Clover.  .  .  . 

Horny  .... 
Starchy.  .  . 

bu. 
67.8 
55.8 

bu. 
56.9 
46.3 

bu. 
10.6 

perct. 
18.6 

Clover  .... 

Horny.  .  .  . 

59.6 

51.2 

North-Central 
(corn,  corn,  spring 
grains,  clover) 

Clover.  .  .  . 

Starchy.  .  . 

Horny.  .  .  . 

Starchy.  .  . 

56.5 

66.8 
52.0 

46.5 

55.9 
41.2 

4.7 
14.7 

9.2 
26.3 

Clover.  .  .  . 

Horny.  .  .  . 

61.7 

53.3 

Starchy.  .  . 

59.6 

49.6 

3.7 

6.9 

2d  yr.  corn 

Horny.  .  .  . 
Starchy.  .  . 

34.0 
23.4 

23.7 
15.,0 

8.7 

36.7 

South-Central 
(corn,  corn,  corn, 
soybeans) 

2d  yr.  corn 
2d  yr.  corn 

Horny.  .  .  . 
Starchy.  .  . 

Horny.  .  .  . 
Starchy.  .  . 

34.9 
32.5 

38.1 
32.2 

26.4 
24.0 

30.4 
22.4 

2.4 
8.0 

9.1 
26.3 

2d  yr.  corn 

Horny.  .  .  . 
Starchy  .  .  . 

41.9 
38.5 

35.7 
30.5 

5.2 

14.6 

eliminated.  Further  data  on  the  value  of  physical  selection  in  main- 
taining and  increasing  yields  will  be  given  following  the  presentation 
of  the  data  bearing  on  resistance  and  susceptibility  of  different  strains 
and  selections  of  corn  to  these  diseases. 

TABLE  60. — YIELDS  OF  CORN  GROWN  FROM  BRIGHT-TIPPED  AND  FROM  BROWN- 
TIPPED  HORNY  SEED,  ALL  OF  WHICH  HAD  BEEN  CLASSED  AS  NEARLY 
DISEASE-FREE  ON  THE  BASIS  OF  ONE  GERMINATION  TEST,  1921 


Location  of 
experiment 

Previous 
crop 

Relative  time 
of  planting 

Acre  yield 

Reduction  from 
brown-tipped 
kernels 

Bright- 
tipped 
kernels 

Brown- 
tipped 
kernels 

Urbana  

Clover  

Early  

bu. 
69.1 
67.6 
66.3 
68.2 
67.5 
71.3 
75.9 
72.7 

bu. 
69.3 
60.8 
61.5 
60.9 
69.7 
65.8 
69.8 
68.4 

bu. 
-0.2 
6.8 
4.8 
7.3 
-2.2 
5.5 
6.1 
4.3 

perct. 
-0.3 
10.1 
7.2 
10.7 
-3.3 
7.7 
8.0 
5.9 

Urbana  

Corn         .... 

Early  

Virginia  

Clover  

Late  .  . 

Bloomington.  .  . 

Corn 

Early 

Bloomington 

Corn 

Early 

Bloomington 

Corn 

Early 

Bloomington.  .  .  . 

Corn  

Early  

Bloomington.  .  .  . 

Corn  

Early  

Mean  reduction  in  acre  yield  of  corn  in  plots  planted  to  brown-tipped  horny  seed, 
4.05  +  .787  bushels. 
4.05 

=  5.15,  odds  greater  than  one  thousand  to  one. 

.787 


1984}  CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES  393 

PART  VI 

SUSCEPTIBILITY  AND  RESISTANCE  TO  THE  ROOT, 
STALK,  AND  EAR  ROT  DISEASES 

EVIDENCES  OF  SUSCEPTIBILITY  AND  RESISTANCE 

The  common  occurrence  thruout  the  corn  belt  of  many  hills  of  corn 
similar  to  the  one  illustrated  in  Plate  VI  suggests  at  once  the  idea  of 
varying  degrees  of  susceptibility  of  corn  plants  to  the  rot  diseases.  In 
most  commercial  fields,  at  least  where  corn  follows  corn  in  the  rota- 
tion, it  is  not  difficult  to  find  hills  in  which  the  roots,  crown,  and  stalk 
of  one  plant  are  badly  affected,  while  another  plant  in  the  same  hill 
apparently  is  not  affected.  At  first  it  was  thought  that  such  condi- 
'tions  might  possibly  be  the  result  of  insect  or  mechanical  injuries,  but 
repeated  examinations  have  shown  that  in  practically  all  cases  the 
trouble  is  caused  by  certain  of  the  root,  stalk,  and  ear  rot  diseases. 
This  occurrence  of  apparently  healthy  and  badly  diseased  plants  in 
the  same  hill  is  evidence  that  some  plants  must  possess  considerable 
resistance. 

Abundant  evidence  of  variation  in  susceptibility  and  resistance 
to  certain  of  these  diseases  has  also  been  found  in  the  germination 
laboratory.  Germinating  kernels  from  some  ears  within  a  given  lot 
may  be  entirely  overrun  with  Rhizopus  spp.  and  other  fungi,  while 
adjacent  kernels  from  other  ears  of  the  same  seed  lot  may  remain  free 
from  the  attack  of  these  organisms  (Fig.  61).  Again,  some  lots  of 
corn  on  the  germinator  may  be  covered  with  fungus  growth,  while 
other  lots  of  corn  on  the  same  tray  and  germinated  under  the  same 
conditions  may  be  entirely  free  from  such  growth,  even  when  spores  of 
Rhizopus  spp.  are  sprayed  on  the  kernels. 

INFLUENCE  OF  HEALTHY  AND  OF  DISEASED  PARENT  PLANTS 

During  the  summer  of  1918  many  controlled  pollinations  were 
made  in  ear-rows  of  Bloody  Butcher  corn  planted  on  heavily  infested 
soil  of  good  fertility.  The  corn  was  all  of  the  same  strain  grown  from 
open-pollinated  seed.  At  harvest  time  careful  descriptions  were  made 
of  the  plants  on  which  the  ears  had  been  artificially  pollinated.  Several 
ears  bearing  first-generation  hybrid  seed  were  obtained,  of  which  both 
staminate  and  pistillate  parents  were  either  badly  diseased  or  ap- 
parently healthy. 

In  1919  these  selected  ears  were  included  in  an  experimental  series 
planted  on  infested  soil  of  medium  fertility.  As  the  kernels  were 
being  dropped  at  planting  time,  half  of  the  hills  were  inoculated  with 
a  pure  culture  of  Gib berella  saubinetii.  The  inoculation  was  made 
by  placing  next  to  the  corn  kernels  a  few  wheat  kernels  overgrown 
with  a  pure  culture  of  this  organism.  The  resulting  yield  data  are 
presented  in  Table  61.  The  corn  grown  from  seed  both  of  whose  par- 


PLATE  VI 

vf 
A         Plant  prematurely  dead  on  account  of  disease. 

B         Plant  maturing  normally. 

In  the  diseased  plant  (A)  the  leaves  are  dying  or  are  already  dead, 
and  the  ear  is  hanging  as  the  result  of  a  crumpled  and  rotted  shank. 
Corn  produced  on  such  plants  is  light  or  chaffy  and  undesirable  for  seed 
purposes. 

In  the  healthy  plant  (B)  the  ear  is  maturing  normally  while  the  leaves 
and  stalk  are  still  green.  Corn  from  such  plants  makes  excellent  ma- 
terial from  which  to  select  good  seed. 


394 


Corn  Root,  Stalk,  and  Ear  Rot  Diseases 


Plate  VI 


Illinois  Agricultural  Experiment  Station 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


395 


ents  were  apparently  disease-free  was  highly  resistant  to  injury  from 
inoculation  with  this  organism.  On  the  other  hand,  the  corn  grown 
from  seed  both  of  whose  parents  were  badly  root-  and  stalk-rotted, 


FIG.     61. — RESISTANCE    AND     SUSCEPTIBILITY     TO 

Rhizopus    SPP.    ON   THE   GERMINATOR 

Germinating  kernels  from  some  ears  will  be 
entirely  overrun  with  Ehizopus  spp.  and  other 
fungi,  while  adjacent  kernels  from  other  ears  from 
the  same  seed  lot  will  remain  free  from  the  attack 
of  these  -organisms. 


396 


BULLETIN   No.   255 


[August, 


was  seriously  affected  by  the  same  inoculation,  the  reduction  in  acre 
yield  amounting  to  19.3  bushels,  or  43.2  percent. 

In  the  light  of  data  presented  later  in  this  bulletin  the  comparative 
acre  yields  of  44.7  and  56.9  bushels  from  the  two  uninoculated  seed 
lots  grown  under  the  same  conditions  on  infested  soil,  may  be  inter- 
preted as  further  evidence  of  a  variation  among  plants  in  their  re- 
sistance and  susceptibility  to  the  corn  diseases. 

During  the  same  season  (1919)  five  other  inoculation  experiments 
were  conducted.  In  one  of  these  experiments  all  the  ear-rows  were 
planted  with  seed  selected  from  apparently  healthy  open-pollinated 
plants.  Seedlings  from  half  these  seed  ears  had  been  nearly  disease- 
free  on  the  germinator  and  those  from  the  other  half  had  been  vig- 
orous but  badly  affected  with  scutellum  rot.  Part  of  the  seed  was  in- 
oculated with  Gibber ella  saubinetii  at  planting  time.  Considerable 
variation  in  effect  was  noted.  Some  of  the  inoculated  rows  grown 
from  nearly  disease-free  seed  were  highly  resistant  under  the  condi- 
tions encountered,  while  others  proved  susceptible. '  Rows  grown  from 
seed  of  strong  vigor  but  badly  affected  with  scutellum  rot  on  the 
germinator  were  very  susceptible  in  the  majority  of  cases  to  injury 
from  inoculation.  Typical  ears  testing  nearly  disease-free  and  rep- 
resenting selections  from  rows  apparently  resistant  and  from  those 
apparently  susceptible,  are  shown  in  Figs.  62  and  63.  These  ears  to- 
gether with  nearly  disease-free  seed  and  moderately  diseased  seed  se- 
lected from  apparently  good  plants  in  the  field  were  used  in  experi- 
ments in  1920  at  DeKalb  and  Martinsville.  The  moderately  diseased 
seed  was  affected  on  the  germinator  with  scutellum  rot,  but  showed 
no  evidence  of  infection  with  either  Diplodia  zeae  or  Fusarium 
monili forme.  The  results  of  these  experiments  are  reported  in  Table 
62  and  shown  in  graph  form  in  Chart  26. 

At  both  DeKalb  and  Martinsville  the  corn  grown  from  the  nearly 
disease-free  seed  selected  from  susceptible  ear-rows  in  the  inoculation 

TABLE   61. — INFLUENCE   OF   COMPARATIVE   RESISTANCE   AND   SUSCEPTIBILITY   OF 
PARENT  PLANTS  ON  THE  RESISTANCE  AND  SUSCEPTIBILITY  OF  PROGENY 
TO  INJURY  BY  SEED  INOCULATION  WITH  Gibberella  saubinetii 

Bloody  Butcher  corn  grown  from  artificially  pollinated  seed  inoculated  at  planting 
time  with  pure  cultures  of  Gibberella  saubinetii.  Infested  soil  of  medium  fertility, 
near  Bloomington,  1919 


Condition  of  parent  plants  from 
which  seed  was  selected 

Acre  yields 

Reduction  in  yield  fol- 
lowing inoculation 

Uninocu- 
lated 

Inocu- 
lated 

Both  parents  apparently  disease-free 

Both  parents  affected  badly  with  root 
and  stalk  rot  diseases  

bu. 
56.9 

44.7 

bu. 
56.5 

2f>    I 

bu. 
0.4 

19.3 

perct. 
0.7 

43.2 

CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


397 


experiment  the  previous  year  was  decidedly  inferior  in  both  total  yield 
and  yield  of  sound  corn  to  that  grown  from  nearly  disease-free  seed 
selected  from  resistant  ear-rows.  At  DeKalb'the  corn  grown  from  the 
good  seed  selected  from  the  resistant  ear-rows  produced  only  6.5 
bushels  of  rotted  and  chaffy  ears  and  nubbins  per  acre,  or  9.9  percent, 
while  the  corn  grown  from  seed  selected  from  the  susceptible  ear- 
rows  produced  16.6  bushels,  or  31.6  percent,  of  unsound  corn.  The 
results  at  Martinsville  were  similar  in  this  respect. 


FIG.  62. — TYPICAL  EARS  FROM  HIGHLY  RESISTANT  EAR-ROWS 

Ears  of  ninety-day  corn  testing  nearly  disease-free  obtained  from  selec- 
tions that  were  quite  resistant  to  injury  by  seed  inoculation  with  G.  saubinetii. 
(Table  62.) 

In  the  experiment  located  at  DeKalb,  where  the  previous  crop  had 
been  clover,  the  difference  between  the  good  and  the  moderately  dis- 
eased field-selected  seed  was  only  3.6  bushels  per  acre,  or  6.2  percent, 
in  favor  of  the  good  seed.  At  Martinsville,  however,  where  corn  fol- 
lowed corn  in  the  rotation,  the  difference  in  yield  of  sound  corn  in 


398 


BULLETIN   No.   255 


[August, 


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Character  of  seed 

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CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


plots  grown  from  the  same  seed  lots  was  6.3  bushels  per  acre,  or  23.9 
percent. 

These  data,  as  well  as  those  presented  in  Table  55,  indicate  that 
nearly  disease-free  seed  of  a  susceptible  strain  or  selection  may  yield 
even  less  than  moderately  diseased  seed  selected  from  apparently  good 
plants  of  a  resistant  strain,  thus  suggesting  the  advantage  of  careful 
plant  selection  and  the  value  of  the  germination  test  in  securing  seed 
which  will  produce  plants  more  highly  resistant.  The  importance  of 


FIG.  63. — TYPICAL  EARS  FROM  SUSCEPTIBLE  EAK-ROWS 

Ears  of  ninety-day  corn  testing  nearly  disease-free  but  obtained  from 
selections  that  were  very  susceptible  to  injury  by  seed  inoculation  with  G. 
saubinetti  (Table  62).  Nearly  disease-free  seed  of  a  susceptible  strain  or  selec- 
tion may  yield  even  less  than  moderately  diseased  seed  selected  from  apparently 
ffood  plants  of  a  resistant  strain. 

comparative  resistance  in  open-pollinated  seed  of  the  same  strain  and 
in  open-pollinated  strains  as  a  whole  is  clearly  emphasized. 

During  the  fall  of  1919  several  hundred  ears  were  selected  from 
plants  the  condition  of  whose  roots  and  stalks  was  carefully  noted  and 
recorded.  All  the  selections  were  made  from  corn  growing  in  the  sec- 


400 


BULLETIN    No.    255 


FIG.  64.  —  SUSCEPTIBILITY  AND  RESISTANCE  TO  THE  CORN  ROT  DISEASES 
At  the  left,  yellow  dent  corn  from  seed  that  tested  nearly  disease-free 
on  the  germinator  but  which  was  selected  from  root-  and  stalk-rotted  plants. 
At  the  right,  the  same  strain  of  corn  grown  from  seed  that  tested  nearly 
disease-free  on  the  germinator  and  which  was  selected  from  apparently 
disease-free  plants.  Disease-free  seed  selected  from  diseased  plants  is  very 
likely  to  produce  plants  more  or  less  susceptible  to  the  corn  rot  diseases. 


60 


Field  selected     field  selected        Field  selected     field  selected 
from  apparently   from  inoculat/on     from  apparent/y  from  inoculation 


good  plants        plots 
Clark.   County 


good  plants         plots 
Deftalb  County 

CHART  26. — RELATIVE  IMPORTANCE  OF  RESISTANT  STRAINS  AND  NEARLY 

DISEASE-FREE  SEED   (Table  62) 

Yields  of  corn  from  nearly  disease-free  resistant  seed  were  larger 
in  each  of  the  experiments  than  yields  from  either  the  moderately  diseased 
resistant  seed  or  the  nearly  disease-free  susceptible  seed.  However,  under 
the  same  conditions  the  moderately  diseased  resistant  seed  outyielded  the 
nearly  disease-free  susceptible  seed. 


1924] 


CORN  BOOT,  STALK,  AND  EAK  ROT  DISEASES 


401 


ond-  and  third-year  corn  following  clover  or  other  sod.  The  following 
winter  ten  kernels  were  tested  from  each  ear  at  three  successive  times. 
On  the  basis  of  the  germination  record  thus  obtained,  the  ears  that 
might  have  been  selected  for  seed  by  most  farmers  or  seedsmen,  were 
classified  as  follows:  (1)  nearly  disease-free  seed  from  apparently 
disease-free  plants,  (2)  nearly  disease-free  seed  from  root-  and  stalk- 
rotted  plants,  and  (3)  seed  from  apparently  healthy  plants  which  was 
100  percent  viable  and  vigorous  in  germination,  but  with  20  percent 
or  more  of  the  seedlings  showing  scutellum  rot  on  the  germinator. 
Ears  that  were  obviously  undesirable  for  seed  were  not  included.  From 
approximately  300  ears  of  good  appearance  that  had  been  selected 
from  badly  root-  and  stalk-rotted  plants,  only  ten  were  found  to  be 
vigorous  in  germination  and  at  the  same  time  free  from  Diplodia  and 
Fusarium  infection  and  not  affected  by  scutellum  rot.  The  physical 
characteristics  of  these  ten  ears,  and  also  those  of  the  nearly  disease- 


TABLE  63. — CERTAIN  PHYSICAL  CHARACTERISTICS  OF  NEARLY  DISEASE-FREE  SEED 

EARS   SELECTED   FROM   DISEASED   AND   FROM   APPARENTLY 

DISEASE-FREE  MOTHER  PLANTS 

Ears  selected  in  October,  1919,  and  planted  in  experiment  reported  in  Table  64 


Characters  observed 


Nearly  disease- 
free  ears  from 
diseased  mother 

plants 
(10  ears) 


Nearly  disease- 
free  ears  from 
apparently  dis- 
ease-free plants 

(62  ears) 


perct. 
Luster 

Bright 10.0 

Intermediate 60 . 0 

Dull 30.0 

Shank  attachment 

Bright 20.0 

Slightly  pink  or  slightly  brown 40 . 0 

Pink  or  brown 40 . 0 

Tip  of  ear 

Covered  by  husk 50 . 0 

Slightly  exposed 20. 0 

Exposed 30.0 

Indentation 

Smooth 10.0 

Intermediate 70.0 

Rough 20.0 

Brightness  of  kernel 

Bright 70.0 

Intermediate 0.0 

Dull 30.0 

Kernel  composition 

Horny 0.0 

Intermediate 100.0 

Starchy 0.0 


perct. 

75.8 

24.2 

0.0 


87.0 

11.4 

1.6 


72.6 

21.0 

6.4 


71.0 

29.0 

0.0 


100.0 
0.0 
0.0 


17.8 

80.6 

1.6 


402  BULLETIN  No.   255  [August, 

free  ears  from  apparently  healthy  plants,  are  given  in  Table  63.  Of 
the  ten  ears  mentioned,  only  two  had  bright  shank  attachments.  The 
disease-free  ears  from  the  badly  diseased  plants  were  duller  in  luster, 
rougher  in  indentation,  and  with  less  horny  endosperm  than  the  dis- 
ease-free ears  from  healthy  plants. 

Seed  from  these  different  groups  of  ears  was  planted  across  a 
series  of  twenty-one  soil  experimental  plots  designated  as  the  Lime- 
stone Series  on  the  farm  of  Mr.  Eugene  D.  Funk.  Twelve  of  these 
soil  plots  had  been  in  clover  sod  for  two  years,  none  of  the  crop  be- 
ing removed  the  second  year.  The  remaining  nine  plots  were  on 
ground  that  had  produced  a  crop  of  spring  wheat  following  corn. 
The  corn  crop  had  been  badly  diseased  and  the  wheat  crop  had  been 
so  heavily  scabbed  that  it  was  not  harvested.  This  soil  is  classified  as 
brown  silt  loam.  It  is  of  medium  fertility  with  good  natural  drainage. 
The  entire  field  was  fall  plowed.  The  resulting  yields  are  presented 
in  Table  64. 

On  the  comparatively  clean  soil  the  difference  in  total  acre  yield 
between  the  disease-free  corn  from  healthy  plants  and  the  disease-free 
corn  from  badly  diseased  plants  was  only  4.0  bushels,  or  85.6  bushels 
as  compared  with  81.6  bushels.  However,  on  heavily  infested  soil,  the 
difference  in  total  acre  yield  from  these  two  seed  lots  was  12.6  bushels, 
or  79.4  bushels  as  compared  with  66.8  bushels.  Differences  in  acre 
yield  of  sound  corn  were  greater ;  namely,  4.8  bushels  on  the  com- 
paratively clean  soil  and  19.4  bushels  on  the  infested  soil. 

The  corn  from  nearly  disease-free  seed  selected  from  apparently 
healthy  plants  yielded  6.7  bushels,  or  8.2  percent,  less  sound  corn  per 
acre  on  the  heavily  infested  soil  than  on  the  comparatively  clean  soil 
(Table  64).  No  doubt  a  part  of  this  reduction  must  have  been  due  to 
the  lower  supply  of  nitrogen  in  the  plots  in  this  part  of  the  experiment. 
However,  the  corn  grown  from  the  nearly  disease-free  seed  selected 
from  badly  root-  and  stalk-rotted  plants  proved  to  be  very  susceptible 
to  injury  on  the  heavily  infested  soil,  yielding  21.3  bushels,  or  27.7 
percent,  less  sound  corn  on  the  infested  soil  than  on  the  comparatively 
clean  soil  (Fig.  64).  Moreover,  it  yielded  no  better  than  corn  grown 
from  seed  lots  affected  with  scutellum  rot,  which  also  were  very  sus- 
ceptible to  injury. 

These  data,  together  with  those  presented  in  Tables  61  and  62, 
show  that  disease-free  seed  selected  from  diseased  plants  is  very  likely 
to  produce  plants  more  or  less  susceptible  to  the  corn  rot  diseases. 
Data  in  Table  64  indicate  that  corn  grown  from  seed  affected  with 
scutellum  rot  may  be  susceptible  to  disease  and  to  injury  from  un- 
favorable soil  conditions.  This  suggestion  is  borne  out  by  data  pre- 
sented in  Tables  74  and  77.  Furthermore,  since  the  nearly  disease- 
free  seed  from  the  badly  diseased  plants  had  more  starchy  endosperm 


1994} 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


403 


TABLE  64. — SUSCEPTIBILITY  OF  DIFFERENT  SEED  SELECTIONS  AS  DETERMINED  BY 
GROWING  ON  COMPARATIVELY  CLEAN  AND  ON  HEAVILY  INFESTED  SOIL 

Yellow  dent  corn  planted  May  17  on  brown  silt  loam,  near  Bloomington,  1920 


Character  of  seed 

Acre  yields 

Reduction  in 
marketable  corn 
on  heavily  in- 
fested soil 

Comparatively 
clean  soil 

Heavily  infested 
soil 

Total 

Sound 

Total 

Sound 

bu. 

bu. 

bu. 

bu. 

bu. 

perct. 

Nearly    disease-free    seed 

from  apparently  disease- 

free  plants  

85.6 

81.7 

79.4 

75.0 

6.7 

8.2 

Nearly    disease-free    seed 

from    root-    and    stalk- 

rotted  plants  

81.6 

76.9 

66.8 

55.6 

21.3 

27.7 

Standard    diseased    corn- 

composite  used  in  1920 

(mostly  scutellum  rot)  . 

74.8 

69.7 

61.8 

53.2 

16.5 

23.7 

Seed  selected  from  standing 

apparently    disease-free 

plants;    100   percent   in 

viability,  but  20  percent 

of  germinated  seedlings 

showed  scutellum  rot.  .  . 

79.6 

"75.2 

62.7 

55.2 

20.0 

26.6 

than  the  nearly  disease-free  seed  from  apparently  healthy  plants,  these 
data  (Table  64)  suggest  that  nearly  disease-free  starchy  seed  may  be 
more  susceptible  to  the  root,  stalk,  and  ear  rot  diseases  than  disease- 
free  horny  seed. 

INFLUENCE  OP  CHARACTER  OF  ENDOSPERM 

During  the  winter  of  1920-1921  two  nearly  disease-free  composites 
differing  widely  in  character  of  endosperm  were  prepared,  the  one 
horny  and  the  other  starchy.  Each  composite  included  kernels  from 
approximately  75  ears.  Ears  with  starchy  kernels  that  were  100  per- 
cent viable,  vigorous  in  germination,  and  at  the  same  time  uninfected, 
are  not  easily  found,  as  most  starchy  ears  are  more  or  less  diseased. 
The  75  ears  from  which  this  nearly  disease-free  starchy  composite  was 
made  were  gradually  accumulated  during  the  germination  tests  of  over 
2,000  bushels  of  seed  corn. 

These  seed  lots  were  planted  on  duplicate  plots  following  clover  and 
following  corn  in  a  rotation  of  corn,  corn,  spring  grains,  and  clover. 
The  yield  data  are  given  in  Table  65.  Altho  the  corn  grown  from 
nearly  disease-free  starchy  seed  was  practically  equal  in  yield  to  that 
from  the  nearly  disease-free  horny  seed  on  the  plot  following  clover, 
the  corn  grown  from  the  same  lot  of  starchy  seed  was  decidedly  in- 
ferior in  yielding  ability  on  the  infested  soil  following  corn,  where 
soil  conditions  were  less  favorable. 


404 


BULLETIN   No.   255 


[August, 


Similar  nearly  disease-free  horny  and  starchy  composites  repre- 
senting a  large  number  of  ears  were  prepared  for  planting  in  1922. 
Nearly  disease-free  starchy  ears  were  even  more  difficult  to  obtain 
than  they  had  been  the  previous  year.  They  represented  a  very  choice 
selection  from  approximately  3,000  bushels  of  seed.  These  two  com- 
posites were  used  in  an  inoculation  experiment  conducted  on  very 
fertile  soil  on  which  a  crop  of  corn  had  been  grown  in  1921.  Previous 
to  that  time  the  land  had  been  virgin  prairie  sod.  Seed  for  part  of 
the  experiment  was  inoculated  by  soaking  it  for  about  thirty  minutes, 
immediately  before  planting,  in  a  water  suspension  of  young  conidia 
of  Gibberella  saubinetii.  The  yield  data  are  given  in  Table  66. 

In  the  uninoculated  part  of  the  experiment  there  was  little  differ- 
ence in  the  total  yields  of  corn  grown  from  nearly  disease-free  horny 
and  starchy  seed,  the  results  being  107.6  ±1.3  bushels  as  compared 
with  109.6  ±  1.3  bushels,  respectively.  However,  the  corn  grown  from 
the  same  two  seed  lots  was  affected  very  differently  by  the  inoculation 
of  the  seed.  The  total  yield  of  corn  from  the  nearly  disease-free  horny 
seed  was  reduced  5.0=b  1.7  bushels,  or  4.6  percent,  while  the  yield  from 
the  nearly  disease-free  starchy  seed  was  reduced  24.4  ±3. 6  bushels,  or 
22.3  percent.  Comparisons  made  with  yields  of  sound  corn  in  this 
experiment  are  practically  in  accord  with  those  of  total  yields. 

These  differences  in  resistance  and  susceptibility  to  injury  from 
seed  inoculation  with  Gibber ella  saubinetii,  one  of  the  organisms  asso- 
ciated with  the  com  rot  diseases,  are  presented  graphically  in  Chart  27. 
These  data,  together  with  those  presented  in  Table  59,  indicate  that 
corn  grown  from  nearly  disease-free  starchy  seed  is  less  resistant  than 
corn  from  nearly  disease-free  horny  seed  not  only  to  pure-culture  in- 


TABLE  65. — COMPARATIVE  RESISTANCE  AND  SUSCEPTIBILITY  OF  NEARLY  DISEASE- 
FREE  STARCHY  AND  HORNY  SEED  AS  DETERMINED  BY  GROW- 
ING ON  CLEAN  AND  ON  INFESTED  SOIL 

Yellow  dent  corn  grown  in  duplicate  plots  on  soil  of  medium  fertility,  University 
South  Farm,  Urbana,  1921 


Character  of  seed 

Acre  yield 

Reduction  following  plant- 
ing on  infested  soil 

Compara- 
tively clean 
soil  (follow- 
ing; clover) 

Infested  soil 
(following 
corn) 

Horny  

bu. 
73.5 
71.1 

70.7 
68.6 

bu. 
63.4 
56.8 

66.0 
56.1 

bu.                  perct. 
10.1                 13.7 
14.3                20.1 

4.7                   6.6 
12.5                 18.2 

Starchy  

Horny        

Starchy  

1924] 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


405 


TABLE  66. — COMPARATIVE  SUSCEPTIBILITY  OF  CORN  GROWN  FROM  NEARLY  DISEASE-FREE 

STARCHY  AND  HORNY  SEED,  TO  INOCULATION  AT  PLANTING  TIME  WITH  A 

PURE  CULTURE  OF  Gibberella  saubinetii 

Yellow  dent  corn  planted  May  26  and  27  on  brown  silt  loam  of  high  fertility, 
near  Bloomington,  1922 


Character 
of  seed 

Number 
of  repli- 
cations 

Mean  acre  yield 

Reduction  in  inoculated  plots 

Uninoculated 

Inoculated 

Total 

Sound 

Total 

Sound 

Total 

Sound 

Horny.  .  . 
Starchy.  . 

12 
6 

bu. 
107.6  ±  1.3 

109.6  +   1.3 

bu. 
100.9  ±1.4 

98.5  +  0.9 

bu. 
102.6  ±  1.1 

85.2  ±  3.4 

bu. 
97.8  ±  1.3 

80.0  +  2.9 

bu. 
5.0  ±  1.7 

24.4  ±  3.6 

perct. 
4.6 

22.3 

bu. 
3.1  ±  1.9 

18.5  +  3.0 

perct. 
3.1 

18.8 

100 


oculations,  but  also  to  injury  under  unfavorable  soil  conditions  that 
exist  where  corn  follows  corn  in  the  rotation.  In  many  instances  corn 
from  such  starchy  seed  has  proved  to  be  inferior  in  yielding  ability 

even  on  soil  of  high  fer- 
tility where  an  approved 
rotation  and  system  of 
farming  has  been  prac- 
ticed for  several  years 
(Tables  57,  58,  and  59). 
Thus  it  is  evident  that 
starchy  seed,  regardless  of 
its  germination  record,  is 
very  likely  to  produce 
corn  more  or  less  suscep- 
tible to  the  attack  of  cer- 
tain parasitic  fungi  and 
to  injury  from  unfavora- 
ble weather  or  soil  con- 
ditions. 


I 


90 


80 


70 


60 


50 


*to 


30 


\ 

1 

0 
CO 

«3 

<S 

to 

^ 

£ 
1 

1 

3 

HORNY 


STARCHY 


CHART  27. — CORN  FROM  STARCHY  SEED  Is  MORE 
SUSCEPTIBLE  TO  INJURY  BY  INOCULATIONS 
WITH  G.  saubinetii  THAN  CORN  FROM 
HORNY  SEED  (Table  66) 


The  above  statement 
does  not  imply  that  horny 
seed  always  is  likely  to 
produce  corn  resistant  to 
these  diseases.  Neither 
does  it  imply  that  all  ears 
with  horny  kernels  are 
desirable  for  seed  pur- 
poses. Horny  seed  may 
carry  considerable  infec- 
tion with  Diplodia  zeae, 


406  BULLETIN   No.    255  [August, 

Fusarium  spp.,  and  Cephalosporium  acrcmonium.  Seed  that  is  in- 
fected with  disease-producing  organisms,  regardless  of  kernel  com- 
position, may  produce  corn  very  susceptible  to  injury  under  some  con- 
ditions. The  important  consideration  is  disease  resistance,  a  condition 
ivhich  up  to  the  present  time  the  authors  have  not  found  associated 
with  starchy  seed  or  infected  horny  seed,  but  rather  generally  asso- 
ciated with  seed  from  apparently  healthy  plants  that  shows  vigor  and 
freedom  from  disease  on  the  germinator  and  that  is  horny  in  com- 
position. 

DIFFERENCES  IN  COMMERCIAL  STRAINS 

During  these  investigations  it  became  evident  that  the  many 
strains  of  yellow  dent  corn,  as  they  are  selected  and  maintained  on 
various  farms  thruout  the  corn  belt,  must  differ  widely  in  their 
yielding  ability  and  resistance  and  susceptibility  to  disease.  Data 
on  which  the  above  statement  is  based  are  presented  in  Table  67 
and  Chart  28.  The  differences  in  the  proportion  of  unmarketable  corn 
(rotted  and  chaffy  ears  and  small  nubbins)  where  the  different  strains 
were  grown  under  the  same  soil  and  climatic  conditions  are  very  sig- 
nificant. In  1921,  the  year  in  which  there  was  much  damage  from 
ear  rots,  Strains  No.  9  and  No.  10  produced  total  acre  yields  of  79.4 
and  78.3  bushels,  respectively.  Yet  the  difference  in  yield  of  sound 
corn  was  20.7  bushels,  or  40.8  bushels  as  compared  with  61.5  bushels. 
Strain  No.  9  produced  38.6  bushels  of  damaged  corn,  while  Strain  No. 
10  produced  only  16.8  bushels.  Since  these  strains  were  grown  on 
adjoining  plots  receiving  the  same  soil  treatment,  these  large  differ- 
ences cannot  be  explained  on  the  basis  of  differences  in  climatic  or 
soil  conditions.  Obviously  they  were  due  to  different  degrees  of  dis- 
ease resistance  and  susceptibility  possessed  by  the  several  strains  of 
corn  in  question. 

Such  a  wide  variation  in  resistance  and  susceptibility  no  doubt  is 
one  very  important  factor  in  determining  the  comparative  yields  of 
different  strains  from  year  to  year.  When  all  the  conditions  are 
favorable  thruout  the  growing  season,  a  strain  of  corn  that  is  normally 
low  in  yielding  ability  may  produce  a  very  satisfactory  yield ;  but 
the  same  strain  under  slightly  adverse  conditions  may  produce  a  very 
low  yield. 

In  this  connection  the  yield  data  from  three  strains  of  corn  entered 
in  the  corn  contest  in  Woodford  County,73  Illinois,  have  considerable 
significance.  The  samples  were  supplied  thru  the  courtesy  of  Mr. 
M.  L.  Mosher  and  members  of  the  Woodford  County  Farm  Bureau. 
Sample  No.  62  was  furnished  by  Mr.  George  Krug.  This  strain  of 
corn  had  been  a  consistently  good  yielder  in  that  county  for  four  con- 
secutive years.  The  ears  submitted  were  rather  smooth  in  indentation, 
horny  in  composition,  and  bright  in  luster.  Sample  No.  77  had  been 


1DS4] 


CORN  ROOT.  STALK,  AND  EAR  ROT  DISEASES 


407 


I! 


408 


BULLETIN   No.    255 


[August, 


developed  by  another  farmer  in  the  same  county.  It  had  been  se- 
lected for  a  specific  kernel  shape  and  indentation,  and  with  special 
emphasis  on  a  minimum  of  space  between  the  rows.  The  ears  sub- 
mitted were  mid-rough  in  denting,  dull  in  luster,  and  with  rather 
starchy  endosperm.  Sample  No.  120  had  been  developed  by  still 
another  farmer  in  Woodford  county.  This  strain  was  the  lowest 
yielder  both  years  in  which  it  was  entered  in  the  contest. 

In  order  to  compare  the  yielding  ability  of  these  three  strains  of 
yellow  dent  corn  under  more  than  one  set  of  conditions,  plantings 
were  made  in  1922  at  Bloomington  and  at  Peoria.  The  results  are 
given  in  Tables  68  and  69.  At  Bloomington  the  soil  and  climatic 
conditions  were  very  favorable  thruout  the  season.  The  field  in  which 

TABLE  67. — YIELDS  FROM  VARIOUS  STRAINS  OF  YELLOW  DENT  CORN  SHOWING 
VARIATIONS  IN  PROPORTION  OF  UNMARKETABLE  EARS 

Experiments  conducted  on  brown  silt  loam  at  various  points  in  Illinois,  1920-1922 


Year 

Location 

Number 
of 

strain 

Character 
of  strain 

Acre  yield 

Total 

Sound 

Unmarket- 
able 

1920 

Bloomington.  .  . 
Bloomington.  .  . 

Bloomington.  .  . 
Bloomington.  .  . 

1 

2 

3 
4 

Susceptible 

bu. 
45.4 
64.4 

56.3 
60.2 

bu. 
30.4 
56.1 

40.0 
54.0 

bu. 

15.0 

8.3 

16.3 
6.2 

perct. 
33.0 
12.9 

29.0 
10.3 

Good  

Susceptible 

Good  

1921 

Bloomington.  .  . 
Bloomington  .  .  . 

Bloomington  .  .  . 
Bloomington.  .  . 

Bloomington.  .  . 
Bloomington.  .  . 

Bloomington.  .  . 
Bloomington.  .  . 

Bloomington  .  .  . 
Bloomington.  .  . 

5 
6 

7 
8 

9 
10 

11 
12 

13 
14 

Susceptible  

104.5 
107.8 

78.3 
90.6 

79.4 
78.3 

71.4 
76.4 

70.7 

82.5 

67.7 

84.2 

51.5 

72.0 

40.8 
61.5 

32.5 
53.0 

43.9 
65.5 

36.8 
23.6 

26  .«8 

18.6 

38.6 
16.8 

38.9 
23.4 

26.8 
17.0 

35.2 
21.9 

34.2 
20.5 

48.6 
21.5 

54.5 
30.6 

37.9 
20.6 

Good  

Susceptible  

Good  

Susceptible 

Good  

Susceptible  .... 

Good  

Susceptible 

Good  

1922 

Bloomington.  .  . 
Bloomington.  .  . 

Bloomington.  .  . 
Bloomington.  .  . 

15 

16 

17 
18 

Susceptible  

102.8 
105.9 

98.4 
101.6 

93.6 
101.2 

85.9 
94.2 

9.2 

4.7 

12.5 

7.4 

8.9 
4.4 

12.7 
7.3 

Good  

Susceptible 

Good 

1922 

Pekin  

19 

20 

Susceptible 

67.5 
72.2 

54.7 
65.6 

12.8 
6.6 

19.0 
9.1 

Pekin   

Good 

1922 

Urbana  

21 
22 

23 
24 

Susceptible 

48.9 
54.5 

53.4 
54.1 

37.3 
46.6 

42.9 
46.0 

11.6 
7.9 

10.5 

8.1 

23.7 
14.5 

19.7 

15  0 

Urbana  

Good.    . 

Urbana  

Susceptible 

Urbana  

Good  

1924} 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


409 


TABLE  68. — YIELDS  FROM  THREE  STRAINS  OF  YELLOW  DENT  CORN 
Planted  May  27  on  brown  silt  loam  of  high  fertility,  near  Bloomington,  1922 


Character  of  seed 

Number 
of 
repli- 
cations 

Mean  acre  yield 

Total 

Sound 

Unmarketable 

Woodford  county  high- 
yielding  No.  62  

18 
18 

18 

bu. 

96.6  ±  1.1 
92.0  +  1.3 
91.3  +  1.4 

bu. 
88.5  +  1.2 
78.8  ±  1.7 
79.2  +  1.3 

bu, 

8.1  +  0.4 
13.2  ±  0.6 
12.1  +  0.6 

perct. 
8.4 
14.3 
13  .  3 

Woodford  county  low- 
yielding  No.  77  

Woodford  county  low- 
yielding  No.  120  

the  experiment  was  conducted  had  produced  only  one  crop  of  corn, 
having  been  in  virgin  prairie  sod  previous  to  that  time.  Altho  Sample 
No.  62  was  in  the  lead,  the  difference  in  total  yield  between  this  corn 
and  the  lowest-yielding  sample  was  only  5.3  ±  1.8  bushels,  a  figure 
which  is  not  very  significant  in  terms  of  the  probable  error  involved. 
The  difference  in  yield  of  sound  corn,  9. 3  ±1.8  bushels,  however,  is 
significant.  Corn  from  both  low-yielding  samples,  No.  77  and  No.  120, 
was  decidedly  more  susceptible  to  ear  rots  than  corn  from  the  high- 
yielding  sample  No.  62,  as  shown  by  the  quantities  of  unmarketable 
corn  from  each,  that  is,  13.2  ±0.6  and  12.1  ±0.6  bushels,  respectively, 
as  compared  with  8.1  ±0.4  bushels.  The  yield  of  sound  corn  from 


100 


Unsound  Corn 


CHART  29. — YIELDS  FROM 
THREE  WOODFORD 
COUNTY  STRAINS 
GROWN  UNDER  FAVOR- 
BLE  CONDITIONS  (Table 
68) 

Under  favorable  condi- 
tions, inferior  strains  may 
compare  favorably  In 
yielding  ability  with  good 
strains. 


High 
Yielding 
No.  6Z 


Low 

Yielding 
No.  77 


Low 
Yielding 
No.  120 


BULLETIN   No.   255 


[August, 


TABLE  69. — COMPARATIVE  RESISTANCE  AND  SUSCEPTIBILITY  OF  THE  SAME  THREE 

STRAINS  OP  YELLOW  DENT  CORN  AS  THOSE  REPORTED  IN 

TABLE  68,  AS  DETERMINED  BY  YIELDS 

Planted  May  29  in  clean  soil  of  high  fertility  and  infested  soil  of  medium  fertility, 
near  Peoria,  1922 


Seed 

Soil 

Acre  yield 

Reduction  in 
sound  corn  on 
infested  soil 

Total 

Sound 

Unmarket- 
able 

Woodford  county             / 
high-yielding,  No.  62  f 

Woodford  county           | 
low-yielding,  No.  77  j 

Woodford  county             * 
low  -yielding,  No.  120  V 

Clean   .... 

bu. 
96.0 

77.8 

91.0 
69.1 

90.9 
61.5 

bu. 
81.7 
69.9 

74.5 
57.3 

70.5 

48.9 

bu. 
14.3 
7.9 

16.5 
11.8 

20.4 
12.6 

perct. 
14.9 
10.2 

18.1 
17.1 

22.4 
20.5 

bu. 
11.8 

17.2 
21.6 

perct. 
14.4 

23.1 
30.6 

Infested.  .  . 
Clean   .... 

Infested.  .  . 
Clean  

Infested.  .  . 

Sample  No.  120  was  slightly  higher  than  that  from  Sample  No.  77 
in  this  experiment,  or  79.2  ±  1.3  bushels  as  compared  with  78.8  ± 
1.7  bushels.  These  data  are  presented  graphically  in  Chart  29. 

At  Peoria  the  same  seed  lots  were  planted  at  the  same  time  on  both 


too 


CHART  30.  —  YIELDS 
FROM  THREE  WOOD- 
FORD  COUNTY 
STRAINS  ON  BOTH 
CLEAN  AND  INFEST- 
ED SOIL  (Table  69) 

Reductions  in  yield 
from  the  use  of  low- 
yielding  strains,  as 
compared  with  a  high- 
yielding  strain,  were 
greater  in  infested  soil 
than  in  clean  soil. 
Also,  reductions  in 
yield  following  plant- 
ings on  infested  soil, 
as  compared  with 
plantings  on  clean  soil, 
were  greater  in  the 
low-yielding  strains 
than  in  the  high-yield- 
ing strain. 


Woodford '  Counfy        Woodford  County      Woodfbnal  County 
High  Yielding  No. 62  Low  folding,  No.77  Low  folding.  No.  120 


3924]  CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES  411 

clean  and  infested  soil  in  adjoining  fields.  Clean  soil  on  the  farm  of 
Mr.  Charles  Gordon  previously  had  been  in  virgin  prairie  sod.  The 
infested  soil  had  produced  a  crop  of  corn  in  1921,  and  had  been  farmed 
for  approximately  forty  years.  Both  soils  have  been  classified  as 
brown  silt  loam.  On  the  clean  soil  the  difference  in  acre  yield  between 
Samples  No.  62  and  No.  120  was  5.1  bushels  in  total  yield  and  11.2 
bushels  in  sound  corn  (Table  69  and  Chart  30).  The  difference  be- 
tween the  same  strains  was  much  greater  on  infested  soil,  being  16.3 
bushels  in  total  yield  and  21.0  bushels  in  sound  corn.  The  reductions 
in  yield  of  sound  corn  due  to  planting  on  infested  soil  as  compared 
with  planting  on  clean  soil  are  very  different  for  the  two  samples, 
being  only  11.8  bushels  for  No.  62  and  21.6  bushels  for  No.  120,  or 
14.4  percent  as  compared  with  30.6  percent.  Sample  No.  120,  which 
produced  at  about  the  same  rate  as  No.  77  on  the  Bloomington  field, 
where  conditions  were  more  favorable,  was  7.6  bushels  below  No.  77 
on  infested  soil  at  Peoria.  Thus  it  seems  that  resistance  and  suscepti- 
bility are  very  important  factors  in  determining  the  relative  merits 
of  various  strains  of  corn. 

The  data  that  have  been  presented  on  disease  resistance  and  suscep- 
tibility furnish  strong  arguments  for  the  adoption  of  resistant  strains 
of  corn  and  of  approved  rotations  in  which  there  is  a  more  liberal  use 
of  legumes. 

PHYSICAL    CHARACTERS    OF    SEED    CORN    ASSOCIATED 
WITH  SUSCEPTIBILITY  AND  RESISTANCE 

From  the  foregoing  data  it  is  evident  that  there  are  many  differ- 
ences in  the  physical  appearance  of  nearly  disease-free  seed  ears  of 
good  viability  and  vigor  in  germination  as  compared  with  infected 
ears  and  ears  the  progeny  of  which  is  susceptible  to  the  corn  rot  dis- 
eases. Outstanding  examples  of  these  differences  in  physical  appear- 
ance are  illustrated  in  Figs.  65  and  66.  Infected  and  nearly  disease- 
free  ears  often  may  be  so  much  alike  in  some  particular  characters, 
such  as  luster,  nature  of  shank  attachment,  exposure  of  tip  of  ear, 
character  of  endosperm,  or  kernel  indentation,  that  no  distinction  based 
on  that  character  can  be  made  between  them,  but  they  seldom  are 
alike  in  all  of  the  above-mentioned  characters. 

SCOPE  OF  EXPERIMENTS 

In  view  of  the  fact  that  such  differences  in  physical  appearance 
do  exist  and  that  ears  from  diseased  plants  frequently  produce  plants 
more  or  less  susceptible  to  disease  and  injury  under  unfavorable  soil 
and  weather  conditions,  a  series  of  experiments  was  planned  during 
the  winter  of  1920-1921,  to  determine  the  need  for  considering  all  the 
physical  characters  under  discussion  in  detecting  seed  ears  which 
produce  plants  that  are  comparatively  resistant,  and  those  which  pro- 


412 


BULLETIN   No.    255 


[August, 


duce  plants  that  are  susceptible  ( 1 )  to  inoculations  with  pure  cultures 
of  certain  of  the  organisms  associated  with  the  root,  stalk,  and  ear  rot 
diseases,  and  (2)  to  injury  from  the  unfavorable  conditions  en- 
countered when  planted  in  heavily  infested  soil.  The  experiments 


FIG.  65. — POOR  SEED 

Representative  moderately  diseased  ears  selected  for  experimental  pur- 
poses from  ears  supplied  by  J.  R.  McKeighan  and  Son,  Yates  City.  (Com- 
pare with  Fig.  66.) 

embraced  an  area  of  approximately  15  acres  of  virgin  prairie  sod  and 
10  acres  of  infested  soil  of  high  fertility,  located  on  the  farms  of  Mr. 
Eugene  D.  Funk  and  Mr.  De  Loss  Funk,  Bloomington,  Illinois. 

DESCRIPTION  OF  SEED 

Four  widely  different  strains  of  yellow  dent  corn  that  had  been 
grown  in  central  Illinois  for  several  years  were  selected  as  a  basis  for 
these  experiments.  These  were  designated  as  Lots  A,  B,  and  C,  and 
the  nearly  disease-free  check.  The  first  three  lots  of  seed  (A,  B,  and 
C)  were  furnished  by  three  representative  farmers  from  as  many 
nearby  counties.  Each  lot  of  seed  was  typical  of  the  seed  these 
farmers  expected  to  plant. 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


41:5 


Altho  Lots  A  and  B  had  not  been  given  much  attention  from  the 
standpoint  of  selection,  Lot  A  for  several  years  had  been  selected  early 
in  the  field  without  particular  attention  to  type  of  plant  and  had  been 
germinated  for  viability.  Also,  in  this  strain  of  corn  fairly  large  ears 
of  rough  indentation  had  been  given  preference.  Lot  C  had  been  se- 


FIG.  66. — GOOD  SEED 

Nearly  disease-free  ears  selected  for  experimental  purposes  from  ears  sup- 
plied by  J.  R.  McKeighan  and  Son,  Yates  City.  (Compare  with  Fig.  65.)  It 
is  evident  that  there  are  many  differences  in  the  physical  appearance  of  nearly 
disease-free  seed  ears  of  good  viability  and  vigor  in  germination  as  compared 
with  infected  ears  and  ears  the  progeny  of  which  is  susceptible  to  the  corn  rot 
diseases. 

lected  over  a  period  of  fifteen  years  for  smooth,  horny,  rather  heavy 
ears.  The  lot  of  nearly  disease-free  check  seed  was  from  a  strain  which 
had  received  six  years'  continuous  selection  for  grain  production  and 
apparent  freedom  from  disease  in  the  field,  and  vigor  and  freedom 
from  infection  on  the  germinator.  During  this  period  the  strain  out 
of  which  the  nearly  disease-free  check  corn  was  chosen  had  become 


414 


BULLETIN   No.   255 


[August, 


horny  in  composition  and  medium  to  smooth  in  indentation.  More 
complete  descriptions  of  these  lots  of  corn  are  given  in  Tables  70 
and  71. 

In  this  series  of  inoculation  experiments  it  was  fundamentally 
important  that  corn  used  for  checks  be  as  nearly  disease-free  as 
possible.  The  particular  120  ears  included  in  this  composite  behaved 
satisfactorily  during  four  germination  tests  of  ten  kernels  each.  This 
group  of  ears  represented  a  most  careful  selection  from  1,500  bushels 

TABLE  70. — CERTAIN  PHYSICAL  CHARACTERISTICS  AND  GERMINATION  RECORDS  OF 

APPARENTLY  SUSCEPTIBLE  AND  APPARENTLY  GOOD  SEED  SELECTIONS  FROM 

LOTS  A  AND  B,  1921 


Lol 

,  A 

Lo 

t  B 

Characters  observed 

Apparently 
diseased 

(238  ears) 

Apparently 
disease-free 
(88  ears) 

Apparently 
diseased 
(100  ears) 

Apparently 
disease-free 

(55  ears) 

Luster 
Bright 

perct. 
10  9 

perct. 
28.4 

perct. 
25.0 

perct. 
35.1 

Intermediate  

67.2 

64.8 

65.0 

61.4 

Dull  

21.9 

6.8 

10.0 

3.5 

Shank  attachment 
Bright  

2.5 

22.7 

8.0 

82.5 

Slightly  pink  or  slightly 
brown       

49.2 

69.3 

30.0 

17.5 

Pink  or  brown  

48.3 

8.0 

62.0  ' 

0.0 

Tip  of  ear 
Covered  by  husk  . 

24.8 

27.3 

30.0 

31.6 

Slightly  exposed 

35  7 

62.5 

28.0 

42.1 

Exposed 

39  5 

10  2 

42.0 

26.3 

Indentation 
Smooth  .           .    . 

14.3 

62.5 

16.0 

68.4 

Intermediate 

33  6 

36.4 

50.0 

31.6 

Rough  

52.1 

1.1 

34.0 

0.0 

Brightness  of  kernel 
Bright  

42.4 

82.9 

61.0 

84.2 

Intermediate 

35  3 

14.8 

28.0 

15.8 

Dull  

22.3 

2.3 

11.0 

0.0 

Kernel  composition 
Horny  

15.5 

70.4 

23.0 

70.2 

Intermediate       .    .    . 

59.3 

28.4 

55.0 

29.8 

Starchy 

25  2 

1.2 

22.0 

0.0 

Germination  record 
Viability  

99.48 

99.34 

99.6 

100.0 

Strong  vigor  

75.38 

84.80 

61.1 

88.0 

Disease 
Scutellum  rot 

47  1 

30  0 

39.1 

30.91 

Visible    Fusarium    infec- 
tion   

3.45 

0.9 

7.4 

2.54 

Visible  Diolodia  infection 

0.0 

0.0 

0.1 

00 

1984] 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


415 


of  corn  that  had  been  plant-selected  in  the  field  for  good  seed.  Their 
viability  was  99.94  percent,  97.22  percent  of  the  seedlings  being  strong 
in  vigor  on  the  germinator  with  good  root  development  (Table  71). 
Only  3.5  percent  of  the  4,800  kernels  tested  developed  the  scutellum 
rot.  There  was  0.05  percent  Fusarium  infection,  but  not  a  trace  of 
Diplodia  infection.  Fig.  67  shows  representative  ears  of  this  same 
strain  of  corn. 

In  the  light  of  the  data  presented  up  to  this  point  selections  of 
apparently  good  seed  and  apparently  susceptible  seed  from  each  of 


TABLE  71. — CERTAIN  PHYSICAL  CHARACTERISTICS  OF  APPARENTLY  SUSCEPTIBLE 

AND  APPARENTLY  GOOD  SEED  SELECTIONS  FROM  LOT  C  AND  FROM  THE 

EARS  COMPRIZING  THE  NEARLY  DISEASE-FREE  CHECK,  1921; 

ALSO  GERMINATION  RECORDS 


Characters  observed 


LotC 


Apparently 
diseased 
(41  ears) 


Apparently 

disease-free 

(58  ears) 


Disease-free 
check 

(120  ears) 


perct. 
Luster 

Bright.  . 12.2 

Intermediate 82 . 9 

Dull 4.9 

Shank  attachment 

Bright 2.4 

Slightly  pink  or  slightly  brown 2.4 

Pink  or  brown 95 . 2 

Tip  of  ear 

Covered  by  husk 7.3 

Slightly  exposed 34 . 2 

Exposed 58 . 5 

Indentation 

Smooth 48.8 

Intermediate 34 . 1 

Rough 17.1 

Brightness  of  kernel 

Bright 46.3 

Intermediate 36 . 6 

Dull : 17.1 

Kernel  composition 

Horny 48.8 

Intermediate 41 . 5 

Starchy 9.7 

Germination  record 

Viability 93  41 

Strong  vigor 65 . 85 

Disease 

Scutellum  rot 12 . 47 

Visible  Fusarium 11 . 22 

Visible  Dinlodia  .  0.97 


perct. 

46.6 

53.4 

0.0 


56.9 

36.2 

6.9 


48.3 
32.8 
18.9 


100.0 
0.0 
0.0 


89.7 
8.6 
1.7 


79.3 

20.7 

0.0 


96.21 
80.18 


8.66 
3.45 
0  34 


perct. 

53.4 

45.1 

1.5 


87.2 

10.5 

2.3 


71.4 

26.3 

2.3 


75.9 

21.8 

2.3 


98.5 
1.5 
0.0 


74.4 

24.8 

0.8 


99.94 
97.22 


3.5 

0.05 
0.0 


416 


BULLETIN   No.   255 


[August, 


the  first  three  lots  (A,  B,  and  C)  were  made  on  the  basis  of  physical 
characters  only,  prior  to  the  germination  test.  No  ear  was  included 
in  the  apparently  good  seed  that  did  not  appear  to  have  matured 
normally  and  fully  on  a  comparatively  healthy  plant.  Kernels  from 
both  ends  and  from  the  middle  of  every  ear  were  examined  and  those 


FIG.  67. — TYPICAL  GOOD  SEED  EARS  USED  IN  THE  1921  EXPERIMENTS 

The  factors  considered  in  the  selection  of  these  ears  were:  character  of 
mother  plants,  protection  by  husks,  condition  of  shank  attachments,  luster  of 
ears,  brightness  of  kernels,  composition  of  kernels,  and  vigor  and  freedom  from 
disease  on  the  germinator. 

ears  showing  any  evidence  of  poor  seed  condition  or  infection  were 
not  included. 

The  selections  of  apparently  susceptible  seed  were  made  up  of 
ears  that  obviously  had  been  produced  on  plants  more  or  less  affected 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


417 


A  O 


^•--*C3> 


A          Q    ^ 


f  - 


FIG.  68. — REPRESENTATIVE  EARS  FROM  THE  GOOD-SEED  SELECTION- 
LOT  A  (Table  70) 


418 


BULLETIN   No.   255 


[August, 


FIG.   69. — REPRESENTATIVE  EARS  FROM  THE  SUSCEPTIBLE  SEED 
SELECTION — LOT  A  (Table  70) 


1924] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


419 


with  the  root,  stalk,  and  ear  rot,  diseases.  No  ears  with  apparently 
poor  seed  condition  or  heavy  infection  were  included.  In  Lots  A  and 
B  the  apparently  susceptible  selection  was  representative  of  about 
90  percent  of  the  entire  sample  of  over  1,000  ears  in  each  case. 

Following  the  selections  on  the  basis  of  physical  appearances  a 
germination  test  was  made  of  30  kernels  from  each  ear.  The  results 
indicated  that  all  the  selections  were  reasonably  good  in  viability  with 
the  exception  of  three  ears  from  the  apparently  susceptible  seed  from 
Lot  C.  These  were  found  to  be  dead  and  accordingly  were  discarded. 


FIG.  70. — REPRESENTATIVE  EARS  FROM  THE  GOOD  SEED  SELECTION 
LOT  C  (Table  71) 


420 


BULLETIN   No.    255 


[August, 


FIG.  71. — EXPERIMENTAL  PLOTS  ON  CLEAN  AND  ON  INFESTED  SOIL 
At  the  right,  the  first  crop  grown  on  virgin  prairie  sod.  At  the  left, 
the  ninth  cultivated  crop  since  virgin  prairie  sod  on  a  field  that  had  pro- 
duced six  crops  of  corn,  one  crop  of  oats,  and  one  crop  of  wheat.  The  soil 
type  and  topography  of  the  two  experimental  fields  were  very  similar. 
(Tables  74,  77,  79,  81)  U.  S.  Department  of  Agriculture  experimental  plots 
on  farm  of  Mr.  E.  D.  Funk,  Bloomington. 

Germination  records  for  the  various  lots,  together  with  a  description 
of  the  physical  characters  of  the  ears,  are  summarized  in  Tables  70 
and  71.  Representative  ears  from  some  of  the  selections  are  shown 
in  Figs.  68,  69,  and  70.  The  increases  in  percentages  of  strong, 
vigorous  seedlings  on  the  germinator,  as  well  as  the  decreases  in  per- 
centages of  diseased  seedlings,  in  the  selections  of  apparently  good 
seed,  are  very  significant.  They  clearly  indicate  the  value  of  such 
physical  selection  in  increasing  vigor  of  germination  and  reducing 
the  percentage  of  infected  ears  and  ears  affected  with  scutellum  rot. 

DESCRIPTION  OF  EXPERIMENTAL  FIELDS 

The  two  fields  chosen  as  the  site  for  these  studies  were  adjoining 
and  were  similar  in  soil  type,  topography,  and  fertility  (Fig.  71). 
One  field  was  virgin  prairie  sod.  The  adjoining  field  had  produced 
corn  six  years,  oats  one  year,  and  wheat  one  year  since  the  virgin 
prairie  sod  had  been  broken  in  1913.  Both  fields  were  fall  plowed. 
As  evidence  of  the  good  fertility  of  the  soil  in  the  cultivated  field  it 
may  be  stated  that  the  wheat  crop  the  preceding  year  yielded  approxi- 
mately 45  bushels  per  acre.  Inasmuch  as  platings  made  from  the 
virgin  soil  did  not  show  the  presence  of  any  of  the  organisms  known 
to  be  parasitic  on  corn,  this  soil  has  been  designated  as  clean,  and  the 
soil  in  the  adjoining  field  as  infested. 

PLAN  OF  EXPERIMENTS 

The  seed  composites  made  from  the  apparently  good  seed  and  the 
apparently  susceptible  seed  selections,  together  with  the  composites 
from  all  the  original  ears  of  each  lot  of  seed,  were  planted  in  groups 
of  four  rows,  the  rows  running  north  and  south.  Every  alternate 
group  of  four  rows  was  planted  with  the  nearly  disease-free  cheek. 
In  each  row  alternate  groups  of  ten  hills  or  rows,  in  some  cases  five 


1924] 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES 


421 


hills,  were  inoculated  at  planting  time  with  Gibber  ella  saubinetii,  the 
wheat  scab  organism,  Fusarium  moniliforme,  and  Diplodia  zeae,  thus 
making  alternate  bands  of  inoculated  and  uninoculated  plots  running 
east  and  west  in  the  field.  These  inoculation  studies  were  conducted 
in  cooperation  with  Dr.  James  G.  Dickson.  When  the  corn  was  about 
32  inches  high,  inoculations  with  Cephalosporium  acremonium  and 
Aplanobacter  steivarti  were  made  by  Dr.  Charles  S.  Reddy  by  means 
ot  hypodermic  injections  near  the  crown  of  the  plant.  The  intervening 
groups  of  ten  hills  or  rows  were  uninoculated  and  were  used  thruout 
the  experiment  as  controls  to  measure  the  effect  of  the  inoculations. 
An  early  and  a  late  planting  were  made  on  both  clean  and  in- 
fested soil  thus  making  four  experiments.  These  four  experiments 
were  identical  in  arrangement  of  seed  and  inoculations,  each  being 
made  up  of  377  plots.  The  seed  planted  in  each  of  these  small  plots 
was  so  selected  that  a  few  kernels  were  included  from  every  one  of 
the  ears  comprising  the  composite  in  question.  For  example  three 
kernels  from  each  of  the  120  nearly  disease-free  ears  were  planted 
in  every  plot  planted  with  check  seed.  The  corn  was  dropped  thru 
specially  designed  hand  planters  at  the  rate  of  three  kernels  per  hill. 
All  necessary  precautions  against  contamination  were  taken  in  con- 
nection with  planting  the  inoculated  seed.  The  mean  field  stands 
secured  from  certain  of  the  composites  in  each  of  the  four  experi- 
ments are  given  in  Tables  72  and  73.  Mean  field  stands  in  the  check 
plots  (Table  73)  ranged  from  92.0  ±  2.5  percent  to  98.9  ±  0.2  percent. 

DISCUSSION  OF  RESULTS 

In  the  above  experiments  the  plants  from  the  apparently  good  seed 
and  those  from  the  apparently  susceptible  seed  were  affected  very 

TABLE  72. — FIELD  STANDS  FROM  ORIGINAL  COMPOSITE 5  AND  APPARENTLY 

SUSCEPTIBLE  AND  APPARENTLY  GOOD  SEED  SELECTIONS, 

BLOOMINGTON,  1921 


Soil 
infes- 
tation 

Date  of 
planting 

Dates  on 
which  stands 
were  taken 

Number 
of 
plots 

Seed 

Mean  field 
stand 

May  11... 

June  11-13.  .  . 

15 
15 
15 

Original  composites  
Apparently  susceptible  .  . 
Apparently  good  

perct. 
92.7  +  0.9 
90.6  +  1.1 
94.4  +  0.7 

Clean.  . 

May  28  ... 

June  16-21  .  .  . 

27 
27 
27 

Original  composites  
Apparently  susceptible.  . 
Apparently  good        .... 

92.1  +  0.7 
91.0  +  0.7 
95.1  +  0.4 

15 

Original  composites  

94.0  +  0.4 

May  10.  .. 

June  14-16  .  .  . 

15 
15 

Apparently  susceptible  .  . 
Apparently  good  

89.7  +  0.8 
94.1  +  0.5 

Infested 

May  30  ... 

June  22-24  .  .  . 

27 
27 
27 

Original  composites  
Apparently  susceptible  .  . 
Annarentlv  srood  

92.9  +  0.5 
89.8  +  0.7 
95.4  +  0.3 

422 


BULLETIN   No.    255 


[August, 


differently  by  the  pure-culture  inoculations,  both  in  the  clean  soil  and 
in  the  infested  soil.  The  data  are  given  in  Table  74.  Data  from 
the  experiments  on  the  clean  soil  are  summarized  in  Table  75  and 
presented  graphically  in  Chart  31. 

The  selections  of  apparently  good  seed  were  much  less  susceptible 
than  was  the  susceptible  seed  to  injury  following  inoculations  with  both 
Gib berella  saubinetii,  a  root-rotting  organism,  and  Cephalosporium 
acremonium,  an  organism  whose  activities  seem  to  be  confined  mostly 
to  the  stalk.  In  plantings  on  clean  soil,  total  yields  and  yields  of  sound 
corn  were  affected  in  approximately  the  same  way.  The  summaries 
given  in  Table  75  and  Chart  31  show  that  the  yield  of  sound  corn 
grown  from  good-seed  selections  was  reduced  by  inoculation  only  5.9, 
5.1,  and  0.2  bushels,  respectively,  for  each  of  the  three  lots  of  seed. 
Yields  of  sound  corn  grown  from  apparently  susceptible  seed  selections 
were  reduced  16.3,  17.0,  and  12.7  bushels,  respectively.  Averaging  all 
the  plots  represented  in  Table  74,  inoculations  reduced  the  yield  of 

TABLE  73. — FIELD  STAND  FROM  NEARLY  DISEASE-FREE  CHECK  SEED, 
BLOOMINGTON,  1921 


Soil  infestation 

Date  of 
planting 

Date  on 
which  stands 
were  taken 

Number 
of  check 
plots  in 
section 

Mean 
field  stand 

Clean 

May  11  

June  11-13 

15 
15 
15 
15 

perct. 
98.6  +  0.3 
97.7  +  1.0 
98.3  +  0.8 
94.2  +15 

15 
15 

15 

94.1  +  1.3 
92.0  +  2.5 
94.0  ±  2.4 

Clean 

May  28 

June  16-21 

15 
15 
15 
15 

98.2  +  0.3 
97.0  +  0.4 
97.1  +  0.5 
97  0  +  0  7 

15 
15 
15 

97.2  +  0.3 
95.4  +  0.4 
98.6  ±  0.2 

Infested 

May  10 

June  14-16 

15 
15 
15 
15 

98.1  +  0.4 
98.5  +  0.1 
98.9  +  0.2 
97  7  +  0  4 

15 
15 
15 

96.0  +  0.8 
96.1  +  0.5 
96.8  ±  0.5 

Infested           .    . 

Mav  30  

June  22-24 

15 
15 
15 
15 

96.8  +  0.5 
98.2  +  0.3 
98.2  +  0.3 
97  7  +  0  3 

15 
15 
15 

98.3  +  0.3 
96.1  +  0.4 
98.8  +  0.3 

1924} 


CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES 


423 


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424 


BULLETIN   No.   255 


[August, 


corn  from  the  good-seed  selections  only  3.7  bushels,  with  odds  of  9  to 
1,  while  the  same  inoculations  reduced  the  yield  of  corn  from  the 
susceptible-seed  selections  15.4  bushels,  with  odds  of  999  to  1  (Table 
76  and  Chart  32). 

On  none  of  the  inoculated  plots  on  clean  soil  were  differences  in 
total  yields  from  the  good-seed  and  from  the  susceptible-seed  selec- 
tions very  large  (Table  74).  However,  differences  in  total  yield  of 
corn  grown  from  the  same  seed  lots  on  the  inoculated  plots  were  very 
significant,  ranging  from  6.1  to  20.7  bushels.  Differences  in  yield  of 

TABLE  75. — SUMMARY  OF  DATA  FROM  TABLE  74  SHOWING  COMPARATIVE 
RESISTANCE  AND  SUSCEPTIBILITY  OF  PLANTINGS  ON  CLEAN  SOIL 


Source 
of 
seed 

Character  of 
seed  selection 

Acre  yield 

Reductions  in 
sound  corn  follow- 
ing inoculation 

Uninoculated 

Inoculated 

Total 

Sound 

Total 

Sound 

Lot  A 

Good 

bu. 
94.4 
89.8 
4.6 

bu. 
69.3 
58.7 
10.6 

bu. 
86.5 
70.5 
Ki.O 

bu. 
63.4 
42.4 
21.0 

bu. 
5.9 
16.3 

perct. 
8.5 
27.8 

Susceptible  

Difference         .  . 

Lot  B 

Good  

83.9 
80.8 
3.1 

60.4 
54.7 
5.7 

80.7 
60.2 
20.5 

55.3 
37.7 
17.0 

5.1 
17.0 

8.4 
31.1 

Susceptible 

Difference  

LotC 

Good  

81.7 
79.9 

1  .X 

58.8 
53.7 
5.1 

77.3 
65.1 
12.2 

o.S.li 
41.0 
17.6 

0.2 
12.7 

0.3 
23.6 

Susceptible  .  .    .  . 

Difference  

sound  corn  in  the  inoculated  plots  of  the  same  experiment  ranged 
from  10.2  to  25.1  bushels. 

Corn  grown  from  good  seed  of  Lot  C  was  little  affected  by  inocu- 
lations with  either  organism,  either  on  clean  soil  or  on  infested  soil, 
but  corn  grown  from  the  apparently  susceptible  seed  was  severely 
affected  by  inoculations  with  Cephalosporium  acremonium.  In  the 
plots  inoculated  with  this  organism  (Table  74)  the  difference  in  total 
yield  between  these  two  seed  selections  was  18.4  bushels ;  but  in  the 
adjacent  uninoculated  plots  the  difference  was  only  2.2  bushels.  The 
difference  in  yield  of  sound  corn  was  three  times  as  large  in  the 
inoculated  plots  as  in  the  uninoculated  plots,  or  25.1  bushels  com- 
pared with  7.8  bushels. 

Total  yields  from  apparently  good-seed  and  from  apparently 
susceptible-seed  selections  were  affected  in  about  the  same  degree  by 
inoculations  with  Gibberella  saubinetii  on  infested  soil.  In  Lot  A 
corn  grown  from  apparently  susceptible  seed  proved  to  be  very  sus- 
ceptible to  injury  from  the  unfavorable  conditions  encountered  in 
the  infested  soil.  The  yield  of  sound  corn  was  reduced  from  63.4 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


425 


bushels  in  clean  soil  to  48.6  bushels  in  infested  soil.  Seed  inoculation 
with  Gibber  ella  saubinetii  did  not  cause  any  further  reduction.  In 
Lots  B  and  C  on  the  infested  soil  inoculations  with  this  organism 
caused  considerably  more  reduction  in  yield  of  sound  corn  in  plots 


Yield  in  Bushels  per  Acre 


Uninoculated •X&Sg  Bushels   Sound  Corn 


Inoculated  K-fr''J   Bushels    Sound  Corn   m?f\m    ( Unsound 


Uninoculated •^-*  Bushels  Sound  Com 


Inoculated  I     >shela  Sound  Cor"  •    (  Unsound 


IJn/rioculuted^K^L^^—^LJ—^—LJ^L-      '•'  '"•  t  Unsound 


Inoculated  ^^^L^^l^SoundCorn        ~.m    ( Unsound 


Uninoculated^*  -  I    >.  Unsound 


Inoculated  •  Bushels  Sound Cornm  (Unsound) 


///W/™/v//,r/E>/y^^a  Bvshe/s   Sound  Corn    1  V..J    I  Unsound 


Inoculated  B^t-  'J^H  [  Unsound 


UninoculatedW^     -.  .  ..'•& M    ( unsound 


Inoculated  ^^^i^f^/^oun^Co^^^^    (  Unsound } 


Reduction  in  Yield  Due  to  Inoculation 


CHART   31. — COMPARATIVE  EFFECT  OF  INOCULATION  ON  GOOD   SEED 
SELECTIONS  AND  ON  SUSCEPTIBLE  SEED  SELECTIONS  (Table  75) 

Yields  from  susceptible  seed  were  reduced  much  more  by  artificial 
inoculations  with  parasitic  organisms  than  yields  from   good  seed. 


426 


BULLETIN   No.   255 


[August, 


TABLE  76. — SUMMARY  OP  DATA  FROM  TABLE  74  SHOWING  COMPARATIVE  RESISTANCE 
AND  SUSCEPTIBILITY  OF  APPARENTLY  GOOD  SEED  AND  APPAR- 
ENTLY SUSCEPTIBLE  SEED  SELECTIONS 


Apparent  character  of 
seed  based  on  physical 
appearance 

Number 
of 
replica- 
tions 

Mean  acre  yield 
of  sound  corn 

Reduction  in 
sound  corn  follow- 
ing inoculation 

Uninocu- 
lated 

Inocu- 
lated 

Good  

6 
6 

bu. 
62.8 
55.7 

bu. 
59.1 
40.3 

bu. 
3.7 
15.4 

perct. 
5.9 

27.7 

odds 
9:1 
999:1 

Susceptible  

grown  from  apparently  susceptible  seed  than  in  those  grown  from 
apparently  good  seed,  the  figures  being  14.7  and  12.3  bushels  as  com- 
pared with  9.5  and  an  increase  of  3.1  bushels.  In  Lot  C  the  differ- 
ence between  the  two  seed  selections  in  yield  of  sound  corn  in  the 
uninoculated  plot  was  4.0  bushels,  while  in  the  inoculated  plot  the 
difference  was  19.4  bushels,  almost  five  times  as  'much.  These  data 
emphasize  the  serious  effect  root  rot  diseases  may  have  in  increasing 
the  percentage  of  chaffy  ears,  rotted  ears,  and  nubbins,  thus  reduc- 


Characfer 
of  seed 


Good 


•Sus- 
ceptible 


Acre  yie/d  of  sound  corn  (bu.) 

20  30  4O  50 60 


CHART  32. — COMPARATIVE 
SUSCEPTIBILITY  TO  IN- 
JURY FROM  ARTIFICIAL 
INOCULATIONS  ( Table 
76) 

The  yield  from  the 
good  seed  was  reduced 
much  less  by  artificial 
inoculation  with  corn  rot 
parasites  than  was  the 
yield  from  the  suscepti- 
ble seed. 


Reduction  in  yield 
following  inoculation 


ing  the  quality  of  the  yield.  These  differences  between  strains  in 
resistance  and  susceptibility  are  very  significant.  Furthermore  these 
differences  could  not  be  measured  by  total  yield  only.  The  impor- 
ance  of  taking  cognizance  of  quality,  as  well  as  quantity,  of  yield  is 
clearly  evident. 

The  difference  in  the  effect  following  the  inoculations  with 
(fibberella  saubinetii  and  with  Cephalosporium  acremonium  on  corn 
grown  from  the  nearly  disease-free  checks  is  worthy  of  consideration. 
On  the  clean  soil  the  organism  affecting  the  roots  (G.  saubinetii) 
caused  a  reduction  of  only  1.9  bushels  in  yield  of  sound  corn.  Six 
years'  continuous  plant  and  germinator  selection  apparently  resulted 
in  isolating  an  open-pollinated  strain  of  corn  highly  resistant  to  this 
organism  under  the  usual  field  conditions.  However,  this  same  strain 


19S4]  CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASKS  427 

of  corn  was  susceptible  to  inoculation  with  Cephalosporium  acre- 
monium,  an  organism  infecting  the  vascular  bundles  of  the  stalk. 
Plants  and  ears  affected  with  this  organism  are  not  always  easily 
avoided  in  the  selection  of  good  seed.  During  the  earlier  years  of  these 
investigations,  when  the  symptoms  of  the  black-bundle  disease  were 
not  understood  and  the  causal  organism  not  known,  it  is  very  likely 
that  many  seed  ears  infected  with  Cephalosporium  acremonium  were 
included  in  the  seed  stock  used  for  propagating  this  strain  of  corn. 
It  would  seem,  therefore,  that  a  program  which  aims  to  develop  pro- 
ductive strains  of  corn  possessing  high  degrees  of  disease  resistance 
must  consider  all  the  factors  concerned.  Yield  data  from  corn  grown 
from  the  nearly  disease-free  check  at  many  places  in  Illinois  and  under 
adverse  conditions  indicate,  however,  that  continuous  selection  for 
production  and  freedom  from  disease  in  the  field  and  vigor  and  free- 
dom from  infection  on  the  germinator  has  been  worth  while  and 
profitable.  Complete  resistance  to  all  the  known  diseases  and  to  injury 
from  adverse  conditions,  combined  with  high  grain  production  and 
maturity,  probably  can  be  attained  only  thru  recombination  of  re- 
sistant inbred  strains  whose  merit  has  been  carefully  determined.  This 
program  will  be  discussed  in  a  following  section. 

Data  are  presented  in  Table  77  on  resistance  and  susceptibility 
of  the  apparently  good-seed  and  susceptible-seed  selections  as  deter- 
mined by  early  and  late  plantings  on  clean  and  infested  soil  of  high 
fertility.  Yields  from  the  good-seed  selection  of  Lot  A  were  reduced 
much  less  by  growing  on  infested  soil  than  those  from  the  apparently 
susceptible  seed,  the  reductions  of  sound  corn  being  9.7  bushels  in  the 
early  planting  and  9.2  bushels  in  the  late  planting  (Table  77)  as  com- 
pared with  14.8  and  20.9  bushels,  respectively.  Differences  in  re- 
sistance and  susceptibility  in  the  two  selections  of  Lot  B  were  not  so 
marked,  but  were  in  favor  of  the  good  seed  in  both  plantings.  In 
Lot  C  the  susceptible  seed  was  only  slightly  below  the  good  seed  in 
yield  from  the  early  planting  on  both  clean  and  infested  soil,  but  the 
yields  from  the  late  planting  from  the  same  seed  lots  showed  that  the 
yield  of  sound  corn  grown  from  apparently  susceptible  seed  was  re- 
duced 8.9  bushels,  or  16.0  percent,  on  the  infested  soil.  Under  identical 
conditions  the  yield  of  sound  corn  grown  from  the  apparently  good 
seed  was  not  affected.  Corn  apparently  resistant  under  some  condi- 
tions may  be  very  susceptible  under  other  conditions.  From  these 
results  it  would  seem,  therefore,  that  the  relative  degrees  of  resist- 
ance and  susceptibility  possessed  by  different  strains  and  selections  of 
corn  cannot  always  be  determined  accurately  by  plantings  on  one  date 
in  one  locality  involving  only  one  set  of  environmental  factors. 

Data  on  the  yielding  ability  of  the  two  selections  from  Lot  A  at 
three  widely  separated  points  in  Illinois  are  given  in  Table  78  and 
Chart  33.  At  all  the  points  mentioned  the  corn  grown  from  the 


428 


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CORN  BOOT,  STALK,  AND  EAR,  EOT  DISEASES 


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430 


BULLETIN   No.   255 


[August, 


apparently  susceptible  seed  proved  to  be  significantly  inferior  to  that 
from  apparently  good  seed,  as  measured  in  acre  yields  of  sound  corn. 
An  analysis  of  all  the  data  presented  up  to  this  point  indicates: 
(1)  that  there  is  usually  a  difference  in  general  appearance  between 
ears  produced  on  diseased  plants  and  those  produced  on  healthy 
plants ;  (2)  that  infected  ears  often  may  be  detected  by  certain  physical 
characters  found  to  be  associated  with  seed  infection  by  one  or  more 
of  the  organisms  associated  with  these  diseases;  and  (3)  that  fully 
matured  and  uninfected  ears  that  have  been  borne  on  apparently 
healthy  plants  usually  produce  corn  possessing  considerable  resist- 
ance both  to  these  diseases  and  to  unfavorable  soil  and  weather  con- 
ditions. The  value  of  considering  all  these  factors  in  selecting  resist- 
ant and  higher  yielding  seed  will  be  discussed  in  the  following  section. 


yield  in  Bushels  per  Acre 


Following       Seed 


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s 


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Susceptible 

Good  U     -Sour/of  Corn 

Susceptible 

Good 
Susceptible 


£  Good 

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Good  •     Sound  Corn 

SuSCeptib/e  •    Sound Corn 


Reduction  in  Yield  of  Sound  Corn 
'='  Due  to  Use  of  Susceptible,  Seed 

CHART  33. — YIELDS  FROM  GOOD-SEED  SELECTIONS  AND  FROM  SUSCEPTIBLE 
SEED  SELECTIONS  (Table  78) 

Reductions  in  yield  of  corn  following  the  use  of  susceptible  seed 
selections,  as  compared  with  corn  from  good-seed  selections,  were  signifi- 
cant in  every  experiment. 


19184]  CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES  431 


Data  presented  in  the  preceding  section  show  that  it  is  possible  to 
choose  from  the  same  seed  lots,  on  the  basis  of  physical  appearance 
alone,  groups  of  ears  the  progeny  of  which  will  differ  widely  in  re- 
sistance and  susceptibility  to  the  corn  rot  diseases  (Table  74).  The 
data  also  show  that  the  better  the  strain  upon  which  the  selection  is 
practiced,  the  greater  the  return  for  the  effort  involved,  for  it  is  only 
by  selecting  from  a  strain  in  which  there  is  some  corn  that  is  resistant, 
that  a  strain  having  a  high  degree  of  resistance  can  be  developed.  In 
the  same  experiments  from  which  these  data  were  secured,  corn  grown 
from  apparently  good  seed  selected  on  the  basis  of  physical  appearance 
was  compared  with  corn  grown  from  the  original  composites. 

DESCRIPTION  OF  SEED 

The  original  seed  composites  in  all  cases  were  made  up  from  the 
seed  lots  as  they  were  received,  that  is,  before  any  selections  were 
made.  Hence  they  contained  seed  from  good  ears  as  well  as  from  ears 
apparently  susceptible  to  disease. 

The  selections  of  apparently  good  seed  represented  the  best  50  to 
90  ears  from  approximately  1,000  ears  in  each  original  seed  lot  of  Lots 
A,  B,  and  C.  These  good  seed  ears  were  chosen  in  much  the  same  way 
that  a  successful  live-stock  man  would  choose  the  best  breeders  from  a 
large  number  of  animals.  In  selecting  such  animals  many  points  would 
be  considered  and  each  given  its  proper  weight  before  any  individual 
would  be  taken  for  breeding  purposes.  Likewise,  in  selecting  ap- 
parently good  seed,  due  emphasis  was  given  to  those  characters  which 
have  been  found  to  be  associated  with  disease  resistance  and  freedom' 
from  infection  (Tables  70  and  71).  Characters  given  major  emphasis 
were  weight  and  size  of  ear,  luster,  appearance  of  shank  attachment, 
nature  of  endosperm,  covering  of  tip  of  ear,  and  kernel  indentation. 
Altho  a  few  of  the  ears  selected  were  perfect  in  all  these  characters,  no 
ears  were  included  that  were  decidedly  deficient  in  any  particular,  in- 
cluding those  characters  indicating  that  the  ears  had  been  borne  on 
diseased  plants.  On  the  basis  of  the  above  physical  characters  alone, 
the  apparently  good  seed  ears  were  the  best  ears  that  could  be  picked 
out  of  each  lot  of  seed.  In  general  appearance  these  good  seed  ears 
(Tables  70  and  71  and  Figs.  67,  68,  and  70)  were  mid-sized,  heavy  in 
weight,  bright  in  luster,  moderately  horny  to  horny  in  kernel  composi- 
tion, and  moderately  smooth  to  smooth  in  indentation.  Shank  at- 
tachments were  bright  or  only  slightly  discolored,  and  in  no  case  was 
there  evidence  of  rotting  of  the  tissues  at  the  butt  of  the  cob.  Tips  of 
the  ears  had  been  covered  by  the  husks  or  had  been  only  slightly  ex- 


432 


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434  BULLETIN   No.   255  [August, 

posed,  as  judged  by  the  appearance  of  the  ear  and  tip  end  of  the  cob. 
A  very  high  percentage  of  the  ears  had  bright  kernels. 

PLAN  OF  INOCULATIONS 

Both  the  original  composite  and  the  selection  of  apparently  good 
seed  from  each  of  Lots  A,  B,  and  C  were  inoculated  with  pure  cultures 
of  Cephalosporium  acremonium,  Aplanobacter  stewarti,  and  Gibberella 
saubinetii.  Inoculations  with  C.  acremonium  and  A.  stewarti  were 
made  by  hypodermic  injection  when  the  corn  was  about  two  feet  high. 
Inoculations  with  G.  saubinetii  were  made  by  immersing  the  seed  im- 
mediately before  planting  in  a  spore  suspension  of  the  organism. 

Reddy  and  Holbert  have  shown  that  C.  acremonium  is  the  cause  of 
the  black-bundle  disease  of  corn  and  that  pure-culture  inoculations 
with  this  organism  are  capable  of  producing  heavy  losses  in  both  dent 
and  sweet  corn.  Seed  infected  with  this  organism  produces  corn  which 
under  certain  conditions,  gives  unsatisfactory  yields.  A.  stewarti  is 
responsible  for  the  bacterial  wilt  disease  of  corn.  G.  saubinetii,  the 
wheat  scab  organism,  has  been  shown  by  Dickson,18- 19  and  by  Koehler, 
Dickson,  and  Holbert,61  to  be  capable  of  causing  seedling  blight  of  corn. 
Undoubtedly,  under  some  conditions,  this  organism  may  cause  con- 
siderable rotting  of  the  roots. 

Data  showing  the  comparative  resistance  and  susceptibility  of  the 
original  composites  and  good-seed  selections  to  inoculations  with  each 
of  these  pathogenic  organisms  are  reported  in  Table  79. 

DISCUSSION  OF  RESULTS 

Corn  grown  from  the  original  composite  from  Lot  A  was  rela- 
tively very  susceptible  to  inoculations  with  both  C.  acremonium  and 
A.  stewarti.  Total  yields  were  reduced  10.7  and  10.9  bushels,  re- 
spectively, and  yields  of  sound  corn,  10.3  and  19.2  bushels.  Good  seed 
selected  from  this  same  lot,  on  the  other  hand,  produced  corn  that  was 
relatively  resistant  to  inoculation  with  either  of  these  organisms  under 
the  conditions  encountered  in  these  experiments.  However,  it  was  not 
nearly  so  resistant  to  injury  from  seed  inoculation  with  G.  saubinetii, 
a  root-rotting  organism,  as  it  was  to  injury  from  the  other  two  organ- 
isms. •  On  clean  soil  the  total  yield  was  reduced  from  93.1  to  80.2 
bushels  by  inoculation  with  G.  saubinetii,  and  the  yield  of  sound  corn 
from  69.5  to  61.5  bushels.  Somewhat  contrary  to  expectations,  in  early 
plantings  on  infested  soil  there  was  only  a  slight  difference  in  the  un- 
inoculated  plots,  either  in  total  yield  or  yield  of  sound  corn,  between 
the  plots  planted  with  the  original  composite  and  those  planted  with 
the  good-seed  selection,  the  figures  being  78.9  as  compared  with  80.3 
bushels  total  yield,  and  58.1  compared  with  60.0  bushels  sound  corn. 
Yields  from  good  seed  were  reduced  more  by  being  planted  on  infested 
soil  than  were  yields  from  the  original  composite,  the  reductions  being 


1924}  CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES  435 

9.5  bushels  as  compared  with  1.2  bushels,  respectively.  On  infested 
soil  reductions  in  sound  corn  following  inoculation  with  G.  saubinetii 
were  less  in  the  plots  planted  with  the  good-seed  selection  than  in  the 
plots  planted  with  the  original  composite,  the  data  being  2.0  bushels, 
or  3.3  percent,  compared  with  7.2  bushels,  or  12.4  percent. 

Considering  yield  of  sound  corn  in  the  uninoculated  plots,  appar- 
ently good  seed  from  Lot  A  was  better  than  the  original  composite 
from  that  lot  in  every  instance  except  one,  where  the  yields  were  the 
same.  In  the  inoculated  plots,  in  three  out  of  four  cases,  yields  of 
sound  corn  from  selected  seed  were  much  greater  than  those  from  the 
original  composite.  This  suggests  that  corn  grown  from  apparently 
good  seed  from.  Lot  A  possessed,  for  the  most  part,  more  disease  resist- 
ance than  corn  grown  from  the  original  composite. 

In  Lot  B  the  plants  from  both  the  original  composite  and  the  ap- 
parently good  seed  were  rather  susceptible  to  infection  by  inoculation 
with  C.  acremonium  as  measured  by  reduction  in  yield  of  sound  corn. 
However,  the  total  yield  of  the  original  composite  was  reduced  more 
than  that  of  the  good-seed  selection,  the  reduction  being  19.9  bushels, 
or  21.9  percent,  as  compared  with  7.7  bushels,  or  9.0  percent. 

Corn  from  the  apparently  good  seed  of  Lot  B  was  less  affected  by 
seed  inoculation  with  G.  saubinetti,  both  in  total  yield  and  in  yield  of 
sound  corn,  than  that  from  the  original  composite.  In  clean  soil  the 
yield  of  sound  corn  from  the  original  composite  was  reduced  9.6 
bushels,  or  15.6  percent,  as  compared  with  a  slight  increase  of  corn 
from  the  good-seed  selection.  In  infested  soil  differences  in  resistance 
and  susceptibility  were  not  so  large  but  were  in  favor  of  corn  from 
the  good  seed.  Yields  of  sound  corn  were  consistently  higher  in  the 
plots  grown  from  selected  seed  than  in  those  grown  from  the  origi- 
nal composite,  both  in  the  inoculated  and  the  uninoculated  plots. 

While  the  plants  in  Lot  B  were  susceptible  to  inoculation  with 
C.  acremonium  and  G.  saubinetii,  they  were  apparently  resistant  to 
inoculation  with  A.  stewarti.  In  the  plots  inoculated  with  this  latter 
organism,  the  increase  in  total  yield  of  corn  grown  both  from  original 
composites  and  from  apparently  good  seed  probably  was  due  to  the 
increase  in  suckering.  Generally,  however,  hypodermic  inoculations 
with  this  organism  did  not  cause  any  appreciable  increase  in  sucker- 
ing.  The  fact  that  corn  grown  from  Lot  B  was  susceptible  to  injury 
when  inoculated  with  C.  acremonium  and  apparently  resistant  when 
inoculated  with  A.  stewarti  emphasizes  a  statement  made  previously 
in  this  bulletin  that  comparative  resistance  to  one  disease  does  not 
necessarily  mean  an  equal  resistance  to  other  diseases  (Table  74). 

It  will  be  remembered  that  Lot  C  came  from  a  strain  of  yellow 
dent  corn  that  had  been  selected  over  a  period  of  years  for  heavy 
ears  with  moderately  smooth  dented,  lustrous  kernels.  This  selection 
undoubtedly  eliminated  most  of  the  ears  with  starchy  kernels  and 


436 


BULLETIN   No.   255 


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1924}  CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES  437 

those  produced  on  plants  with  badly  rotted  roots.  But  such  a  selec- 
tion would  not  necessarily  be  effective  in  culling  out  ears  from  plants 
slightly  affected  with  the  black-bundle  disease  or  any  of  the  bacterial 
diseases.  Corn  grown  from  original  composites  of  Lot  C  was  very 
susceptible  to  inoculations  with  both  C.  acremonium  and  A.  stewarti. 
Total  yields  were  reduced  15.5  and  15.9  bushels,  respectively,  and 
yields  of  sound  corn  12.5  and  28.7  bushels  (Table  79).  Corn  from 
the  carefully  selected  composite,  however,  apparently  was  resistant 
to  inoculation  with  A.  stewarti.  It  was  also  much  less  susceptible 
to  injury  from  C.  acremonium  than  corn  from  the  original  composite, 
the  reduction  in  yield  of  sound  corn  being  3.7  bushels  and  12.5 
bushels,  respectively. 

On  clean  soil  corn  from  neither  the  original  composite  nor  the 
selected  composite  was  affected  appreciably  by  seed  inoculation  with 
the  wheat  scab  organism,  G.  saubinetii.  In  comparing  the  differences 
between  the  yields  of  sound  corn  from  the  good-seed  and  from  the 
original  composite,  it  is  found  that  in  three  out  of  four  cases  the  dif- 
ferences are  much  greater  in  the  inoculated  than  in  the  uninoculated 
plots.  These  data  indicate  that  corn  grown  from  the  good-seed  selec- 
tion was  more  disease  resistant  and  higher  yielding  than  corn  from 
the  original  composite. 

The  data  presented  in  Table  79  are  summarized  in  Table  80.  It 
will  be  noted  that  the  acre  yield  of  sound  corn  grown  from  the  good- 
seed  selection  was  reduced  less  following  each  of  the  inoculations  than 
was  the  acre  yield  of  sound  corn  grown  from  the  original  selections. 

Yields  from  a  large  number  of  plots  planted  with  the  original 
composites  and  good-seed  selections  are  reported  in  Table  81.  These 
data  were  secured  from  early  and  late  plantings  on  both  clean  and 
infested  soil  of  high  fertility.  Data  from  adjacent  plots  planted  with 
nearly  disease-free  check  seed  are  included  in  this  table  as  a  means 
of  comparison. 

Mention  has  been  made  regarding  the  preparation  of  nearly 
disease-free  check  seed  for  1921.  In  this  connection  it  is  well  to  em- 
phasize again  the  fact  that  this  strain  of  corn  had  been  selected  con- 
tinuously since  1916  for  heavy  grain  production  and  apparent  free- 
dom from  disease  in  the  field,  and  for  vigor  and  freedom  from  infec- 
tion on  the  germinator.  In  field  selection  special  attention  was  given 
to  taking  only  well-matured  ears,  which,  were  neither  small  nor  ex- 
ceptionally large,  on  sound  shanks  (Fig.  72)  at  a  convenient  height, 
and  from  erect  sturdy  plants  whose  leaves  were  still  partially  green 
and  free  from*  chlorophyll  reduction,  spotting s,  streamings,  rust,  roll- 
ing, and  crinkling.  Ears  from  smutted  plants  were  avoided  because 
it  has  been  shown  that  resistance  and  susceptibility  to  this  fungous 
disease  is  inherited.  Ears  with  starchy  kernels  were  eliminated.  On 
the  germinator,  seedling  vigor  was  sought  as  much  as  freedom  from 


438 


BULLETIN   No.   255 


[August, 


FIG.  72.- 


-A  WELL  MATURED  EAR  PRODUCED  ON  A  HEALTHY  STALK  AND  A 
SOUND,  STIFF  SHANK 


disease.  No  attempt  was  made  to  have  all  seed  ears  conform  to  any 
previously  determined  standard  of  size  or  shape.  Every  year  a  large 
quantity  of  -seed  was  selected  from  40  to  80  acres  of  corn  that  had 
been  planted  with  carefully  prepared  seed  of  this  strain.  The  nearly 
disease-free  check  seed  was  prepared  from  these  supplies  of  plant- 
selected  material  by  a  careful  selection  on  the  basis  of  physical  appear- 
ance and  performance  on  the  germinator.  Good  seed  remaining  after 
experimental  needs  for  the  current  season  had  been  satisfied  was 
planted  in  large  isolated  fields  from  which  similar  material  could 
be  secured  the  following  year.  In  short,  the  nearly  disease-free  check 
seed  used  in  the  experiments  reported  in  Tables  81  and  82  represented 
the  best  from  a  strain  of  corn  the  development  of  which  embraced 
the  practices  of  plant  selection,  physical  selection,  and  germinator 
selection,  over  a  period  of  years,  with  every  effort  to  insure  broad 
breeding  of  the  open-pollinated  strain  under  development. 

In  Lots  A,  B,  and  C,  it  will  be  recalled  that  selection  of  the  good 
seed  on  the  basis  of  physical  appearance  was  confined  to  a  considera- 
tion of  the  characters  of  the  seed  ear  and  represented  only  one  year's 


1924]  CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES  439 

work  in  that  direction.  These  lots  of  corn,  as  well  as  Lot  D,  de- 
scribed and  discussed  later,  probably  are  typical  of  many  seed  stocks 
found  on  farms  of  the  corn  belt. 

The  good-seed  selection  produced  slightly  higher  field  stands  than 
the  original  composite  in  ten  of  the  twelve  comparisons  reported  in 
Table  81.  Altho  a  good  field  stand  witJi  reference  to  quantity  is 
absolutely  essential  to  satisfactory  yield,  within  limits  it  is  not  so  im- 
portant as  quality  of  stand  as  regards  vigor  and  resistance  of  plants. 
Plantings  from  good-seed  selections  not  only  resulted  in  somewhat 
better  stands,  but  in  stands  with  higher  percentages  of  strong,  vigor- 
ous plants.  Data  previously  published  indicate  that  this  increase  in 
percentages  of  strong,  vigorous  plants  contributed  much  more  to  the 
higher  yields  in  those  plots  than  did  the  slightly  increased  stands.48 

Field  stands  in  plots  planted  with  nearly  disease-free  check  seed 
not  only  were  high,  ranging  from  95.9  ±  0.5  to  98.2  ±  0.2  percent, 
but  contained  very  few  weak  plants. 

Data  in  Table  79  show  that  in  most  cases  corn  grown  from  good- 
seed  selections  was  more  resistant  to  inoculation  with  G.  saubinetii 
and  to  hypodermic  inoculations  with  C.  acremonium  and  A.  stewarti 
than  was  corn  grown  from  the  original  composites.  Undoubtedly, 
the  different  degrees  of  resistance  possessed  by  corn  grown  from  the 
original  composites  and  from  the  good-seed  selections  would  be  very 
important  contributing  factors  in  determining  their  relative  yield- 
ing abilities.  With  every  condition  favorable,  the  good-seed  selec- 
tions might  not  be  expected  to  yield  any  more  than  the  original 
composites,  but  under  somewhat  adverse  conditions  differences  in 
yield  would  be  greater,  as  judged  on  the  basis  of  data  on  the  be- 
havior of  nearly  disease-free  horny  and  starchy  seed  (Tables  57,  58, 
and  59)  and  also  the  performance  of  corn  grown  from  apparently 
susceptible-seed  selections  and  apparently  good-seed  selections  as 
shown  in  Tables  74  and  77. 

In  Lot  A  (Table  81)  corn  grown  from  the  good-seed  selections 
was  higher  in  yielding  ability  than  corn  grown  from  the  original 
composites  both  in  the  plantings  on  clean  soil  and  in  the  plantings 
on  infested  soil.  The  increase  of  8.6  bushels  in  total  yield,  with 
odds  of  113  to  1,  is  significant,  as  is  the  increase  of  8.0  bushels  with 
odds  of  587  to  1.  The  increase  of  1.6  bushels,  with  odds  of  6  to  1, 
however,  is  not  significant.  Increases  in  yield  of  sound  corn,  13.0, 
12.6,  and  15.1  bushels,  with  odds  ranging  from  587  to  1  to  greater 
than  9999  to  1,  beyond  doubt  are  significant.  The  fact  that  the  good- 
seed  selection  showed  no  increase  on  infested  soil  in  the  early  plant- 
ing is  in  accord  with  data  presented  in  Table  75.  It  will  be  remem- 
bered that  the  good-seed  selection  was  comparatively  susceptible  to 
G.  saubinetii,  an  organism  which  is  more  pathogenic  at  the  lower  soil 
temperatures  existing  at  the  time  of  the  early  planting,  May  10. 


440 


BU.LLETIN   No.   255 


[August, 


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19*4] 


CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES 


441 


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442 


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1924}  CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES  443 

In  Lot  B  the  good-seed  selection  gave  no  increase  in  yield  over 
the  original  composite  in  the  early  plantings  on  either  clean  or  in- 
fested soil.  In  late  plantings,  however,  the  good-seed  selection  pro- 
duced a  significant  increase  of  6.3  bushels  in  total  yield  and  6.5 
bushels  in  sound  corn.  On  infested  soil  there  was  an  insignificant 
decrease  in  total  yield,  but  a  material  increase  in  sound  corn,  6.0 
bushels,  or  13.4  percent,  with  odds  of  35  to  1. 

In  Lot  C  the  good-seed  selection  yielded  practically  the  same  as 
the  original  composite  in  every  instance  except  the  late  planting  on 
infested  soil.  The  increase  in  that  plot  of  8.1  bushels  of  sound  corn, 
with  odds  of  16  to  1,  is  scarcely  large  enough,  in  consideration  of  the 
odds  involved,  to  be  very  significant.  Data  presented  in  Table  79 
show  that  the  original  composite,  as  well  as  the  good-seed  selection, 
was  comparatively  resistant  to  inoculations  with  G.  saubinetii.  Fur- 
thermore, Lot  C  came  from  a  strain  of  corn  that  had  been  selected 
for  several  years  for  a  heavy  ear,  with  intermediate  to  smooth  kernel 
indentation.  In  view  of  the  fact  that  corn  from  the  good-seed  selec- 
tion was  much  more  resistant  to  inoculations  with  both  C.  acremonium 
and  A.  stewarti  than  corn  from  the  original  composite,  plantings 
involving  more  adverse  environmental  conditions  might  have  resulted 
in  some  advantage  for  corn  grown  from  the  good-seed  selection. 

Nearly  disease-free  composites  from  Lots  A,  B,  and  C,  did  not 
show  any  increase  in  either  resistance  or  yielding  ability  over  the 
good-seed  selection.  Yield  data  indicated  that  in  these  three  lots  of 
seed  careful  selection  on  the  basis  of  physical  appearance  was  as 
effective  as  selection  on  the  basis  of  performance  on  the  germinator 
in  finding  the  more  resistant  and  higher  yielding  corn  in  the  original 
seed  stocks.  Using  the  original  composite  of  each  lot  as  a  basis  for 
comparison,  selection  on  the  basis  of  physical  appearance  did  not 
decrease  the  yield  of  sound  corn  significantly  in  a  single  instance, 
and  in  six  out  of  the  twelve  comparisons  it  resulted  in  material  in- 
creases in  yield,  five  of  which  were  significant  in  consideration  of 
the  odds  involved. 

The  data  in  Table  81  are  summarized  further  in  Table  82  and 
presented  graphically  in  Chart  34.  The  increases  in  yield  of  sound 
corn  from  the  good-seed  selections  over  the  original  composites  of 
5.8  bushels  on  the  clean  soil  and  7.3  bushels  on  the  infested  soil  are 
very  significant  in  terms  of  the  probable  errors  involved.  The  in- 
creases in  yield  of  sound  corn  of  the  nearly  disease-free  checks  over 
the  good-seed  selections  also  are  significant. 

LIMITATION  OF  THE  VALUE  OF  PHYSICAL  SELECTION  OF  SEED  EARS 

Selection  of  seed  on  the  basis  of  physical  appearance  has  limita- 
tions as  well  as  possibilities  in  that  it  presupposes  not  only  a  variation 


444 


BULLETIN   No.   255 


[August, 


iii  the  seed  stock  but  also  the  fact  that  some  of  the  ears  are  good 
for  seed.  Obviously  good  seed  cannot  be  selected  from  a  strain  of 
corn  that  is  uniformly  susceptible  to  disease  and  to  injury  under 
unfavorable  environment.  Some  strains  of  corn  are  so  susceptible 
to  disease  and  so  deficient  in  those  qualities  which  make  for  high 
yield  of  sound  corn  that  neither  physical  selection  nor  germinator 
selection  can  effect  any  improvement  in  either  quality  or  quantity 
of  the  crop.  Several  such  strains  of  yellow  dent  from  different  farms 
thruout  the  corn  belt  have  been  encountered  during  the  course  of 
these  investigations.  Field  data  from  Lot  D,  one  of  these  strains 
apparently  lacking  possibilities  for  improvement,  are  reported  in 
Table  83. 

Lot  D  came  from  a  strain  of  yellow  dent  corn  that  had  been 
selected  over  a  period  of  years  for  uniformity  of  type,   an  ideal 


/oo 


CHART    34. — VALUE   OF    SELECTING    SEED    ON    THE    BASIS    OF 

PHYSICAL  APPEARANCE   (Table  82) 

The  selecting  of  seed  ears  on  the  basis  of  physical  appear- 
ance is  a  very  important  operation  in  the  preparation  of  seed 
corn.  The  nearly  disease-free  seed  represented  the  best  from  a 
strain  of  corn  the  development  of  which  embraced  the  practices 
of  plant  selection,  physical  selection,  and  germinator  selection 
over  a  period  of  years. 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


445 


^^.^S**«H^- 


»    ***^  .>'*••* 
I.,     -«-  jr 


FIG.  73. — REPRESENTATIVE  EARS  FROM  LOT  D  OF  THE  SELECTED 
COMPOSITE      (See  Table   83) 


446  BULLETIN   No.   255  f August, 

which  the  farmer  had  almost  attained,  but  at  the  sacrifice  of  quali- 
ties more  profitable.  Two  representative  ears  are  shown  in  Fig.  73. 
Inasmuch  as  there  were  no  ears  in  the  seed  lot  that  measured  up  to 
the  standard  used  in  selecting  the  apparently  good  seed  from  Lots  A, 
B,  and  C,  it  was  impossible  to  make  such  a  selection  from  Lot  D. 
All  ears  in  the  original  composite  were  given  three  germination  tests 
of  ten  kernels  each  and  those  showing  the  least  infection  and  the  most 
seedling  vigor  on  the  germinator  were  used  in  a  selected  composite. 

The  selected  composite  from  Lot  D  in  every  case  gave  an  ap- 
preciable increase  in  field  stand  over  the  original  composite  (Table  83) . 
Increases  in  either  total  yield  or  yield  of  sound  corn,  however,  were 
not  significant  except  in  one  instance.  Selection  both  on  the  basis 
of  physical  appearance  and  on  performance  on  the  germinator  was 
ineffective  in  finding  better  seed  in  Lot  D.  The  fault,  however,  prob- 
ably lay  in  the  corn  rather  than  in  the  methods  of  selection. 

In  developing  resistance  to  the  stalk  and  root  rot  diseases  and 
an  increased  productivity,  a  single  year's  selection  on  the  basis  of 
physical  appearance  could  not  be  expected  to  be  so  effective  as  con- 
sistent selection  toward  the  same  goal  over  a  period  of  years.  The 
value  of  continuous  selection  over  a  period  of  years  toward  any  one 
character  is  well  proven  in  the  corn-breeding  experiments  initiated 
by  Dr.  Cyril  G.  Hopkins  and  carried  on  by  Dr.  L.  H.  Smith.  A  com- 
parison of  field  data  from  the  apparently  good-seed  selection,  which 
had  had  no  previous  selection  toward  disease  resistance,  and  from 
the  nearly  disease-free  check,  which  had  been  selected  a  number  of 
years  toward  disease  resistance,  is  interesting  and  instructive  at  this 
point.  In  ten  of  the  twelve  comparisons  (Table  81)  the  increases  in 
yield  of  sound  corn  from  the  nearly  disease-free  check  were  signifi- 
cant, the  odds  ranging  from  555  to  1  to  greater  than  9999  to  1.  Corn 
grown  from  the  check  seed  also  gave  significant  increases  both  in  total 
yield  and  yield  of  sound  corn  over  that  grown  from  the  composite 
selected  out  of  Lot  D  (Table  83).  Corn  grown  from  the  nearly 
disease-free  check  seed  yielded  at  a  higher  rate  in  every  instance  than 
corn  grown  from  apparently  good-seed  selections. 

Altho  selection  of  seed  ears  on  the  basis  of  physical  appearance 
has  its  limitations,  it  is  a  fundamental  operation  in  any  program 
for  the  developing  of  a  strain  of  corn  which  will  be  more  highly 
resistant  to  disease  and  to  injury  under  unfavorable  weather  and 
soil  conditions.  However,  data  indicate  that  the  greatest  improve- 
ment in  resistance  and  productivity  may  be  expected  to  accrue,  not 
from  physical  selection  of  seed  ears  alone,  but  also  from  the  con- 
tinuous practice  of  plant  selection  and  germinator  selection,  always 
beginning  with  a  strain  which  has  possibilities  for  improvement. 


19X4]  CORN  BOOT,  STALK,  AND  EAR  EOT  DISKASES  447 

PART  VII 
A  PROGRAM  OF  CORN  IMPROVEMENT 

During  recent  years  important  developments  have  occurred  in  the 
theory  and  practice  of  corn  breeding.  Investigations  of  inheritance 
in  this  plant  have  resulted  in  putting  corn  improvement  on  a  more 
scientific  basis.  The  once  popular  ear-to-row  method,  which  was 
markedly  effective  in  some  cases,  has  been  discarded  by  many  practical 
corn  breeders.  The  recent  work  on  corn  root,  stalk,  and  ear  rots  has 
emphasized  the  necessity  of  considering  disease  resistance  in  any  corn 
improvement  program  for  the  com  belt.  The  need  for  improvement 
and  the  opportunities  in  corn  breeding  are  believed  to  be  as  great  as 
ever.  The  time  is  considered  opportune,  therefore,  for  outlining  briefly 
a  corn-breeding  program  in  the  light  of  these  developments. 

The  choice  of  the  foundation  stock  for  a  program  of  corn  improve- 
ment is  essentially  a  choice  of  variety.  Varieties  differ  greatly  not 
only  in  such  characters  as  color  of  grain,  time  of  maturity,  and 
tendency  to  sucker,  but  also  in  the  degree  of  adaptation  to  certain 
soils  and  climatic  conditions,  and  in  the  relative  resistance  to  certain 
fungous  diseases  and  insect  pests.  Even  strains  within  a  variety  may 
show  differences  which,  in  some  cases,  are  wider  than  those  between 
so-called  varieties. 

A  variety  should  be  chosen  that  is  well  adapted  to  the  local  en- 
vironmental conditions.  It  should  mature  well;  it  should  be  of  a 
type  that  is  not  discriminated  against  commercially ;  and  it  should  be 
sufficiently  variable  to  show  possibilities  of  improvement.  The  common 
varieties  grown  in  the  various  sections  of  the  country,  in  most  cases, 
are  well  adapted  to  the  conditions  in  those  sections.  Some  strains,  how- 
ever, may  have  a  low  average  production  as  compared  with  others,  or 
may  respond  only  feebly  to  a  program  of  improvement.  Attention  at 
the  outset  to  the  foundation  stock  to  be  used  is  essential  to  success. 

TWO  METHODS  OF  IMPROVING  CORN 

Two  methods  for  corn  improvement  are  suggested.  The  first  em- 
phasizes the  importance  of  selection  as  a  method  of  improvement.  It  is 
particularly  adapted  to  the  corn  grower  who  desires  a  simple  but 
effective  method  of  improving  his  own  crop.  It  also  is  adapted  to  the 
seed-corn  producer  who  has  built  up  a  trade  in  seed  corn  with  his 
neighbors  because  of  his  integrity  and  his  ability  to  select  good  seed, 
handle  it  properly,  and  sell  it  at  a  reasonable  price.  Many  farmers 
do  not  care  to  take  the  trouble  and  time  necessary  to  get  good  seed,  and 
are  quite  willing  to  pay  others  to  do  it  for  them.  The  seed-corn  grower 
can  therefore  be  of  distinct  service  to  his  community  and  at  the  same 
time  develop  a  good  business  for  himself. 


448  BULLETIN   No.   255  [August, 

The  second  is  called  the  pure-line  method.  It  is  believed  to  have  a 
distinct  place  in  a  program  of  corn  improvement  because  of  its  possi- 
bilities. By  this  method  it  would  appear  possible  to  produce  hybrid 
strains  that  are  resistant  to  at  least  a  majority  of  the  diseases  affecting 
corn ;  that  are  adapted  to  the  special  conditions  obtaining  in  different 
sections  of  the  state,  such  as  soil  types,  soil  acidity,  dry  weather,  lengths 
of  season,  and  insect  attack  (the  chinch-bug  and  European  corn  borer)  ; 
and  that  are  adapted  to  special  uses,  such  as  for  silage  production, 
grain  production,  and  manufacturing  purposes  (oil  content).  The 
pure-line  method  is  fundamentally  sound  in  theory,  but  the  practical 
benefits  from  its  use  are,  in  the  main,  still  to  be  realized. 

THE  SELECTION  METHOD 

Selection  of  seed  is  probably  more  effective  in  corn  than  in  any 
other  crop.  This  is  due,  no  doubt,  to  the  nature  of  the  corn  plant. 
Naturally  cross-fertilized,  it  is  continually  producing  hybrids,  which,  in 
turn,  cross  among  themselves,  giving  rise  to  a  multitude  of  types  thru 
recombination  of  characters.  Hence,  in  any  cornfield  a  considerable 
array  of  different  types  is  presented.  Some  of  these  are  desirable 
because  they  are  vigorous  and  productive ;  others  are  undesirable  be- 
cause they  are  weak  in  stalk  and  root,  barren,  or  susceptible  to  dis- 
eases. It  is  this  great  amount  of  variation  in  the  corn  plant  that  fur- 
nishes an  adequate  basis  for  improvement. 

Much  can  be  accomplished  in  the  improvement  of  corn  by  paying 
particular  attention  to  the  plant  in  the  field  and  to  the  ear  in  the  seed- 
house  and  on  the  germinator.  Selection  at  these  three  stages  plays 
the  most  important  part  in  the  process  of  securing  seed  for  the  fol- 
lowing crop.  If  this  work  were  carefully  and  intelligently  done  year 
after  year  on  every  farm,  the  average  corn  yield  for  the  state  would 
be  materially  increased. 

Improvement  of  the  corn  crop  by  the  method  of  selection  suggested 
here  is  simply  and  easily  accomplished.  The  method  commends  itself 
to  corn  growers  who  have  neither  the  time  nor  the  inclination  to  per- 
form complicated  experiments  on  their  own  farms.  It  involves  no 
record-keeping  and  no  harvesting  of  single  rows  or  other  small  areas. 
It  is  effective,  nevertheless,  in  improving  the  corn  crop  in  total  yield 
of  grain  because  it  results  in  the  gradual  elimination  of  weak  types 
and  of  those  susceptible  to  the  corn  rots. 

In  corn  improvement,  special  emphasis  should  be  placed  on  the 
quality  of  grain  produced.  What  is  most  desired  is  not  high  yield 
alone  but  high  yield  of  high  quality  corn.  Selection  for  disease-re- 
sistant corn  according  to  the  method  outlined  below  results  not  only 
in  improvement  in  total  yield,  but  also  in  an  increase  in  the  propor- 
tion of  sound,  marketable  grain. 


1924}          CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES  449 

SELECTING  THE  PARENT  PLANT 

It  has  long  been  recognized  that  the  parent  plant,  as  well  as  the 
seed  ear,  should  be  considered  in  selecting  seed  corn  (Fig.  74).  Evi- 
dence presented  in  this  bulletin  has  placed  greater  emphasis  on  this 
point.  A  diseased  stalk  is  not  likely  to  produce  disease-resistant 
seed.  Moreover,  a  study  of  the  parent  plant  enables  one  to  consider 
other  characters,  such  as  vigor  and  degree  of  maturity,  which  are 
especially  important  in  production. 

The  parent  plant  should  have  an  erect  stalk,  indicating  a  strong 
root  system.  It  should  be  strong,  vigorous,  and  healthy,  free  from 
smut,  rust,  and  other  diseases,  with  the  leaves  free  from  spottings, 
streakings,  and  purplings.  The  stalk  and  portions  of  the  leaves  should 
still  be  green.  The  husks  should  be  dry  and  dead  and  they  should  be 
long  enough  to  cover  the  tip  of  the  ear  completely.  The  ear  should  be 
borne  at  a  height  on  the  stalk  convenient  for  husking,  and  on  a  strong 
shank  of  medium  length.  The  angles  which  the  ears  form  with  the 
stalk  should  range  from  approximately  45°  to  135°.  Upright  ears  are 
likely  to  have  large,  coarse  shanks,  while  ears  hanging  straight  down 
are  usually  borne  on  small,  weak,  broken,  or  diseased  shanks.  Neither 
extreme  is  desirable. 

A  parent  plant  answering  the  above  description  is  likely  to  be 
relatively  free  from  infection  by  the  corn-rot  organisms  and  ordinarily 
will  produce  an  ear  which  likewise  is  relatively  disease-free. 

SELECTING  SEED  EARS 

Results  of  experiments  conducted  at  this  Station  and  elsewhere 
indicate  that  well-matured  ears  are  best  for  seed,  as  their  kernels  are 
more  likely  not  only  to  germinate  well  and  produce  strong  plants  but 
also  to  yield  better  than  those  from  immature  ears.  In  order  to  select 
such  well-matured  ears,  and  at  the  same  time  to  give  due  attention  to 
the  parent  plant  with  special  reference  to  disease,  the  field  should  be 
carefully  inspected  in  the  fall  before  a  killing  frost  for  the  purpose  of 
locating  healthy,  vigorous  plants  that  are  maturing  normally.  If  the 
field  inspection  is  delayed  until  all  the  plants  are  dry  and  dead,  it  is 
difficult  to  distinguish  those  plants  that  matured  normally.  Ears 
selected  from  normally  maturing  plants  will  be  found  to  be  sounder 
and  better  matured,  on  the  whole,  than  those  from  plants  that  are 
diseased. 

The  mere  fact  that  ears  are  selected  in  the  field  prior  to  harvest, 
with  some  attention  to  the  parent  plant,  is,  however,  no  assurance  that 
they  will  make  better  seed  ears  than  those  selected  at  harvest  time  or 
even  from  the  crib,  for  much  depends  on  the  care  exercised  in  selecting 
the  plant  and  in  the  handling  of  the  ears  afterward.  Furthermore,  it 
must  be  recognized  that  the  majority  of  corn  growers  pick  their  seed 
corn  at  the  time  of  harvest,  and  that  they  have  obtained  good  results 


450 


BULLETIN   No.   255 


[August, 


FIG.  74. — PLANT  SELECTION — AN  IMPORTANT  OPERATION 
Note  the  erect  habit,  the  strong,  vigorous,  healthy  ap- 
pearance of  the  plants,  and  the  manner  in  which  the  ears 
are  borne,  indicating  healthy  shanks.  It  has  long  been 
recognized  that  the  parent  plant,  as  well  as  the  seed  ear, 
should  be  considered  in  selecting  seed  corn. 


WU] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


451 


from  this  practice.  As  this  method  is  so  practical  and  inexpensive,  it  no 
doubt  will  continue  to  be  widely  used ;  it  should  not  be  condemned  so 
long  as  it  results  in  the  selection  of  normally  matured  ears  that  show 
good  germination  and  relative  freedom  from  disease.  This  method 
offers  opportunity  to  choose  from  all  the  ears  in  the  field,  since  all  are 
actually  seen  and  handled.  Furthermore,  many  ears  that  would  be 


FIG.  75. — THREE  DEGREES  OF  INDENTATION 

The  ear  on  the  left  represents  the  upper  limit  of  the  smooth  class.  The 
center  ear  represents  the  upper  limit  of  the  class  variously  called  medium, 
intermediate,  and  mid-rough.  Ears  between  these  two  in  indentation  would 
be  classed  as  medium.  The  ear  on  the  right  illustrates  the  rough,  starchy  type. 
Avoid  this  type  in  ear  selection. 


452  BuWiETiN   No.   255  [August, 

taken  for  seed  in  the  early  fall  would  undoubtedly  be  rejected  at  the 
time  of  harvest  because  their  seemingly  good  early  appearance  belied 
their  appearance  when  fully  matured.  However,  it  is  not  advisable  to 
select  seed  ears  very  late  in  the  harvest  period.  Freezing  temperatures, 
together  with  abundant  moisture,  especially  if  followed  by  warmer 
weather,  will  not  only  injure  the  germination  of  the  seed  but  also  pro- 
vide favorable  conditions  for  infection  and  growth  of  fungi.  At  just 
what  date  in  the  fall  harvest  selection  of  seed  ears  should  be  discon- 
tinued must  be  decided  individually  by  each  corn  grower  in  the  light 
of  conditions  affecting  his  own  crop. 

Four  to  five  times  as  many  ears  should  be  picked  for  seed  as  will 
finally  be  used.  This  will  allow  the  rejection  of  ears  because  of  their 
appearance,  or  because  of  poor  or  weak  germination,  or  the  presence  of 
disease.  Much  can  be  gained  by  having  abundant  opportunities  to 
discard  the  less  desirable  ears  in  the  final  selection,  and  this  is  pos- 
sible only  in  cases  where  large  numbers  of  ears  are  on  hand. 

Characteristics  of  Good  Seed  Ears 

That  there  is  a  relation  between  the  general  appearance  of  the  ear 
and  its  ability  to  yield  is  shown  by  the  results  reported  in  this  bulletin. 
This  relationship  appears  to  be  based  largely  on  resistance  and  sus- 
ceptibility to  the  corn  root,  stalk,  and  ear  rot  diseases.  Nearly  dis- 
ease-free ears  ordinarily  can  be  distinguished  from  diseased  ears  by 
their  general  appearance,  for  the  presence  of  disease  interferes  with 
the  normal  activities  of  the  plant,  and  this  interference  is  reflected  in 
the  color,  luster,  texture,  and  indentation  of  the  kernels.  A  knowledge 
of  this  relationship  is  of  distinct  value  to  the  corn  breeder,  for  by  it 
he  can  examine  in  a  short  time  a  large  number  of  ears  and  quickly 
eliminate  from  further  handling  all  but  the  very  best. 

Disease-free  or  nearly  disease-free  ears  have  thick,  plump,  bright, 
clean  kernels  with  well  developed  germs,  intermediate  to  smooth  in- 
dentation, and  distinctly  horny  endosperm  (Figs.  75  and  76).  Such 
ears  are  sound  and  solid,  have  a  bright,  rather  oily  appearance,  and 
give  every  evidence  of  complete  and  normal  maturity.  Shank  attach- 
ments are  white,  bright,  and  free  from  any  discoloration  due  to  ex- 
posure or  disease.  All  ears  that  do  not  measure  up  to  these  standards, 
or  as  many  as  the  seed  stock  will  allow,  should  be  discarded,  as  they 
probably  are  more  or  less  diseased. 

In  selecting  corn  for  seed  to  continue  the  strain,  all  the  points  that 
are  recognized  as  characteristics  of  good  seed  ears  should  be  consid- 
ered. Ears  superior  in  one  characteristic,  such  as  shank  attachments 
for  example,  may  be  inferior  in  kernel  texture  and  luster.  Such  ears 
should  be  rejected  in  favor  of  ears  which  rank  high  in  all  three  .char- 
acteristics. When  choosing  an  animal  for  breeding  purposes,  not  one 


19X4} 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


453 


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454 


BULLETIN   No.   255 


[August, 


but  all  the  points  commonly  recognized  as  belonging  to  animals  of 
merit  are  carefully  considered.  Straight  back,  strong,  well-set  legs, 
bright  eyes,  quality,  intelligence,  disposition,  and  like  characteristics 
are  noted  with  especial  care.  Superiority  in  all  is  desired  because  it 
is  recognized  that  each  plays  its  part  in  the  making  of  a  superior 
animal.  The  same  principle  holds  true  in  the  selection  of  grain  of 
any  kind  that  is  to  be  used  for  seed. 

VALUE  OF  GERMINATOR  SELECTION 

When  circumstances  permit,  the  ears  that  have  been  selected  on 
the  basis  of  their  appearance  should  be  tested  on  the  germinator 
(preferably  the  lime-sawdust  table  germinator)  in  order  to  detect  those 
ears  that  have  high  viability  and  seedling  vigor  and  that  are  freest  from 
the  corn  rot  diseases. 

There  is  considerable  evidence  that  the  germinator  is  especially 
useful  also  in  detecting  ears  that  are  resistant  to  scutellum  rot,  resist- 
ance to  which  seems  to  be  closely  correlated  with  resistance  to  certain 
soil  fungi  and  unfavorable  environmental  conditions.  Thus  the  ger- 


FIG.  77. — A  PROFITABLE  COMBINATION  OF  PROPER,  SEED  SELECTION  AND  GOOD 

FARMING 

A  commercial  field  of  corn  grown  from  seed  that  had  been  carefully 
field  selected  from  vigorous  healthy  stalks  and  severely  culled  on  the  basis 
of  physical  appearance.  The  selections  were  made  from  a  strain  of  yellow 
dent  that  had  been  carefully  selected  over  a  period  of  years  according  to 
recommendations  set  forth  in  this  bulletin.  Farm  of  Mr.  Ed.  Main,  Knox 
county. 


CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES  455 

mination  test  may  be  very  helpful  in  determining  which  are  the  best 
ears  to  use  for  seed. 

The  germination  test,  to  be  reliable,  must  be  conducted  under 
reasonably  uniform  conditions  of  temperature  and  moisture,  and  the 
results  must  be  rightly  interpreted.  Many  corn  growers  either  do  not 
have  the  proper  facilities  for  conducting  such  a  test,  or  are  unable  to 
read  and  interpret  the  results  correctly.  Emphasis  must  then  be 
placed  on  plant  and  ear  selection. 

Since  ears  that  have  been  carefully  selected  in  the  field  and 
properly  cared  for  can  usually  be  depended  on  to  germinate  well  and 
to  show  relatively  little  disease,  lack  of  facilities  for  the  germination 
test  should  not  be  considered  a  great  handicap.  Moreover,  the  limita- 
tions of  the  germination  test  should  be  clearly  recognized.  The  use  of 
the  germinator  will  not  always  lead  to  improvement  in  all  strains  of 
corn,  for  some  strains  are  incapable  of  further  improvement,  either 
because  of  defective  heredity  or  because  of  their  being  in  a  relatively 
homogeneous  condition.  Other  strains  may  be  but  slightly  infected 
with  the  root  rot  organisms  because  of  light  infestation  of  the  soil  in 
which  they  were  grown  or  because  of  a  partial  resistance  to  such  in- 
fection resulting  from  conscious  or  unconscious  selection  for  resistance 
over  a  period  of  years.  The  primary  purposes  of  the  germinator  are 
to  show  the  presence  or  absence  of  disease  and  the  vigor  or  lack  of 
vigor  of  the  seedlings.  If  these  purposes  are  not  accomplished,  then 
the  germinator  is  of  no  aid  in  the  improvement  of  corn. 

THE  PURE-LINE  METHOD 

In  the  improvement  of  corn  by  the  selection  method  just  described, 
the  ear  was  considered  the  basis  of  selection.  Emphasis  was  placed  on 
a  careful  study  of  the  plant  which  produced  the  ear,  i.e.,  the  female 
parent;  the  individual  male  parents  could  not  be  studied  because 
they  are  unknown. 

It  is  commonly  accepted  that  the  male  parent  is  equally  important 
with  the  female  so  far  as  the  transmission  of  hereditary  characters  is 
concerned.  All  the  kernels  on  an  ordinary  ear  of  corn  have  the  same 
female  parent  but  not  the  same  male  parent.  Some  kernels  may  be  the 
result  of  self-fertilization,  others  the  result  of  fertilization  by  pollen 
from  neighboring  plants  in  the  same  or  in  adjacent  hills,  and  still  others 
may  have  resulted  from  fertilization  by  pollen  brought  by  the  wind 
from  more  distant  plants.  The  several  male  parents  of  the  kernels  on 
an  ear  of  corn  presumably  differ  greatly  in  their  hereditary  constitu- 
tion. Hence,  it  is  clear  that  the  kernels  may  be  quite  different  from  each 
other  even  tho  borne  on  the  same  cob  and  by  the  same  female  parent. 

Corn  breeders  are  coming  to  recognize  the  need  of  making  the 
individual  kernel  the  basis  of  selection  rather  than  the  individual  ear 
if  progress  in  corn  improvement  is  to  be  most  rapidly  and  efficiently 


456  BULLETIN   No.   255  [August, 

accomplished.  This  means  that  the  pollen  parent  must  not  only  be 
known  but  also  controlled — the  male  as  well  as  the  female  parent  must 
be  selected.  In  order  to  do  this,  it  is  necessary  to  control  the  pollen 
parent  by  artificial  self-pollination. 

As  a  result  of  continued  self-fertilization,  the  vigor  and  yield 
decrease  quite  rapidly  at  first,  then  more  and  more  slowly  until  finally 
a  point  is  reached  where  no  further  deterioration  is  observed.  The 
strain  is  then  said  to  be  pure,  and  it  will  continue  to  breed  true  there- 
after for  an  indefinite  period  if  no  mixing  occurs  with  other  types. 

A  close  study  of  the  lines  resulting  from  self-fertilization  brings  out 
the  fact  that  some  are  good,  others  are  poor,  and  still  others  are  of 
indifferent  value  so  far  as  capacity  for  production  is  concerned.  Since 
all  the  plants  in  any  one  line  are  alike  genetically,  the  corn  breeder  is 
confronted  with  the  necessity  of  making  a  choice  of  the  best  lines 
rather  than  of  the  best  plants  as  was  the  case  in  the  selection  method. 
Obviously,  the  best  lines  are  those  that  possess,  characters  favorable 
to  production,  such  as  resistance  to  disease  and  lodging,  and  that  are 
themselves  good  producers  of  grain  or  of  forage. 

The  next  step  toward  improvement  is  to  combine  into  one  type  the 
favorable  factors  which  have  been  separated  by  self-fertilization.  This 
is  hybridization.  A  combination  of  two  lines  constitutes  a  single  cross, 
four  lines  a  double  cross,  and  many  lines  a  multiple  cross.  In  the  case 
of  the  single  cross,  best  results  are  obtained  by  making  the  cross  anew 
each  year,  while  in  the  case  of  the  double  and  multiple  crosses  it  would 
appear  possible  to  carry  over  the  benefits  of  hybridization  into  the 
second,  third,  and  subsequent  hybrid  generations  by  careful  selection. 

Briefly,  then,  the  pure  line  method  involves  first  the  purifying  of 
strains  by  inbreeding  and  then  the  building  up  of  a  new  and  vigorous 
strain  by  outcrossing  with  other  desirable  pure  lines. 

INBREEDING  REVEALS  TRUE  CHARACTER  OF  STOCK 

Self-fertilization  (or  inbreeding)  furnishes  a  means  of  eliminating 
various  weaknesses  in  the  stock,  such  as  susceptibility  to  smut  and 
other  diseases,  weak  root  system  (Fig.  78),  blighting,  rolling  of  leaves 
(Fig.  79),  partial  loss  of  chlorophyll  and  various  other  deficiencies  that 
result  in  reduced  growth  and  productiveness.  Inbreeding  reveals  both 
the  good  and  the  bad  characters.  It  spreads  out  before  the  corn  breeder 
the  characteristics  of  the  stock  so  that  he  can  study  them,  select  the 
good,  and  discard  the  poor.  It  brings  to  light  undesirable  qualities  that 
would  otherwise  be  covered  up  by  desirable  ones.  In  thus  showing  the 
true  character  content  of  the  stock,  self-fertilization  in  corn  is  par- 
ticularly valuable  as  a  method  of  breeding  (Figs.  80,  81,  and  82). 

In  corn,  self-fertilization  usually,  if  not  always,  is  accompanied  by 
such  deleterious  effects  as  poor  germination,  reduced  vigor  of  growth, 
disease  susceptibility,  and  lessened  production  of  pollen,  all  of  which 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


457 


FIG.  78. — ERECT  AND  BADLY  LODGED  INBRED  STRAINS 

Strains  with  inherently  weak  root  systems  may  be  eliminated 
by  self-fertilization  and  selection. 

contribute  to  the  general  effect  of  reduction  in  vigor  and  yield  in  plants 
that  are  otherwise  normal.  This  general  reduction  in  the  plant's 
activities  begins  with  the  first  year  of  self-fertilization  and  nearly  al- 
ways becomes  more  marked  with  subsequent  self-fertilization.  Some 
inbred  strains  become  so  weakened  that  they  can  be  propagated  only 
with  difficulty,  particularly  if  grown  on  soil  infested  with  the  corn  rot 
organisms  (Fig.  83).  Other  strains,  however,  show  themselves  to  be 
inherently  stronger  and  more  resistant  to  disease,  and  are  able  not  only 
to  survive  but  also  to  produce  fair  yields  of  seed. 

It  must  not  be  thought,  however,  that  self-fertilization  is  in  itself 
detrimental,  or  that  it  is  the  cause  of  the  accompanying  reduction  in 
general  vigor.  The  cause  must  be  sought  in  deficiencies  of  various  kinds 


458 


BUJjLETIN     NO.     255 


[Au,gust, 


naturally  present  in  the  stock,  and  in  the  principle  that  self-fertilization 
in  a  hybrid  brings  about  a  separation  or  assortment  of  favorable  growth 
factors  into  different  lines.  When  all  such  deficiencies  have  been 
eliminated  and  the  growth  factors  have  been  rendered  pure  by  repeated 
inbreeding,  no  further  reduction  in  vigor  occurs.  Self-fertilization 
may  be  continued  indefinitely  thereafter  with  no  further  detrimental 
effects. 

Eecent  observations  and  experiments  are  directing  attention  to  the 
physiological  behavior  of  selfed  lines  of  corn.  There  are  indications 
that  some  lines  are  able  to  make  more  efficient  use  of  conditions  of 
growth  than  others.  For  example,  some  are  more  efficient  users  of 
phosphorus.  Some  lines  are  able  to  resist  chinch-bugs  to  a  greater 
or  less  extent;  others  are  resistant  to  prolonged  drouth,  on  account 
of  an  extensive  and  efficient  root  system ;  still  others  show  differences 
in  proportion  of  grain  to  stover.  As  methods  of  testing  selfed  lines 
become  more  exact  and  refined,  the  corn  breeder  will  be  able  to  take 
advantage  of  all  the  variations  in  physiological  behavior  which  Nature 
has  provided,  and  to  combine  them  in  crosses  to  secure  the  best  results. 


FIG.  79. — LEAP  ROLLING — A  HERITABLE  WEAKNESS 
Leaf  rolling  is  a  weakness  found  in  many  open-pollinated  strains. 


1924] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


459 


FIG.  80. — A  GOOD  INBRED  STRAIN  OP 
FAMILY  A 


FIG.  81. — A  GOOD  INBRED  STRAIN  OF 

FAMILY  B 

Note  the  sturdiness  of  the  stalks.  If  these  were  growing  in  a  field  of  ordi- 
nary corn,  one  would  have  difficulty  in  distinguishing  them  from  open-pollinated 
plants. 

Valuable  inbred  strains  may  differ  widely  in  their  vegetative  growth  and 
general  appearance. 

The  most  difficult  part  of  the  pure-line  method  is  the  production 
of  the  selfed  lines,  and  on  account  of  the  training,  time,  and  equip- 
ment required,  the  work  will  probably  be  done  largely  by  the  Experi- 
ment Station  and  the  professional  plant  breeder.  However,  since 
different  lines  are  required  for  different  sections  of  the  state  because 
of  varying  soil  and  climatic  conditions,  the  task  of  finding  lines 
adapted  to  them  would  be  greatly  aided  if  there  were  in  each  section 
at  least  one  man  having  the  requisite  training  for  and  inclination 
toward  this  special  field  of  work. 

HYBRIDIZATION  OF  INBRED  STRAINS 

Outcrossing  is  the  normal  habit  of  the  corn  plant.  In  the  ordinary 
cornfield,  cross-pollination  (or  hybridization)  is  the  rule  and  self- 
fertilization  the  exception.  Crossing  between  different  plants  is  en- 
couraged by:  (1)  the  separation  of  tassels  (male)  and  silks  (female)  ; 
(2)  the  difference  in  time  of  maturity  of  pollen  and  silks  on  the  same 
plants;  and  (3)  the  fact  that  the  pollen  is  so  effectively  scattered  about 


460 


BuiiETiN   No.   255 


[August, 


FIG.  82. — AN  INBRED   STRAIN  CHAR- 
ACTERIZED BY  BROAD  LEAVES 

Inbreeding  is  valuable  in  bring- 
ing to  light  desirable  characters  such 
as  this,  which  can  be  combined  in 
crosses  with  others  equally  desirable. 


the  field  by  the  wind.  Nature, 
then,  would  appear  to  favor  any 
method  of  improvement  for  corn 
which  necessitates  a  considerable 
amount  of  outcrossing. 

Just  as  self-fertilization  in  corn 
usually  is  accompanied  by  reduced 
vigor  and  yield,  so  the  hybridized 
condition  gives  increased  vigor  and 
yield.  Hybridization,  therefore,  is 
a  means  of  restoring  the  vigor  lost 
as  a  result  of  self-fertilization. 
Hybrids  between  self-fertilized 
lines  (or  "selfed"  lines)  usually 
exceed  either  parent  in  yield  and 
oftentimes  outyield  even  the  vari- 
ety from  which  the  parent  lines 
originated  (Figs.  84,  85,  and  86). 
However,  hybrids  between  common 
varieties  of  corn  that  have  not  been 
subjected  to  inbreeding  usually 
show  very  little  or  no  increase  un- 
less they  differ  from  each  other  in 
several  characters,  and  even  in  such 
cases  it  is  questionable  whether 
they  give  sufficient  increases  to 
justify  their  use. 


Experience  has  shown,  as  pointed  out  above,  that  it  is  possible  to 
find  selfed  lines  that  show  very  little  reduction  in  yield  and  vigor 
compared  with  the  original  strain  or  variety.  These  lines  are  good 
because  they  contain  a  sufficient  number  of  genetic  factors  favorable 
for  growth  and  productiveness.  With  continued  self-fertilization  they 
would  be  rendered  genetically  pure  for  the  factors  they  contain.  It  is 
highly  improbable  that  all  factors  possessed  by  any  two  such  lines 
would  be  identical.  If  Type  I  contains  factors  A,  B,  and  C,  Type  II 
might  contain  factor  A  but  have  factors  D  and  E  instead  of  B  and  C. 

With  the  large  number  of  factors  responsible  for  vigor  and  pro- 
ductiveness in  corn,  it  is  quite  possible  to  obtain  many  types  that  differ 
among  themselves  with  respect  to  such  factors.  As  a  result  of  these 
differences  in  factors,  the  types  themselves  show  differences  in  such 
characters  as  extent  of  root  development,  height  of  plant,  general  vigor 
of  growth,  and  relative  resistance  to  the  corn  rot  diseases  and  to  smut. 
One  type  may  be  particularly  good  in  certain  of  these  characters, 
another  in  others,  and  so  on.  If  all  such  characters  could  be  com- 


1924} 


CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES 


461 


bined  by  crossing,  the  resulting  type  should  be  superior  to  all  others 
in  yield  and  vigor. 

SINGLE  CROSSES 

The  combination  of  any  two  lines  into  one  results  in  what  is  known 
as  a  single  cross.  Oftentimes  the  hybrid  is  markedly  superior  to  either 
of  the  lines  composing  it.  This  is  particularly  true  if  the  parent  lines 
differ  from  each  other  in  several  respects.  In  such  case  there  are  not 
only  the  beneficial  effects  in  the  hybrid  of  the  bringing  together  of 
desirable  characters,  but  also  the  stimulation,  or  hybrid  vigor,  which  is 
generally  so  pronounced  when  unlike  types  are  crossed.  Some  lines 
show  relatively  few  obvious  differences,  yet  when  crossed  the  hybrid 
is  far  superior  to  either  parent.  This  means  that  selfed  lines  may  differ 
considerably  in  the  genetic  factors  that  control  their  response  to  en- 
vironmental conditions  without  at  the  same  time  differing  in  ap- 
pearance. 


FIG.  83. — MISSING  HILLS  RESULTING  FROM  THE  EARLY  DEATH  OP 

BLIGHTED  AND  BADLY  DISEASED  PLANTS 

Some  inbred  strains  become  so  weakened  that  they  can  be 
propagated  only  with  difficulty,  particularly  if  grown  on  soil 
infested  with  the  corn-rot  organisms. 


462 


BULLETIN   No.   255 


[August, 


FIG.    84. — A    GOOD    CROSS   OF    Two    INBRED    STRAINS 

First-generation  cross  of  the  inbred  strains  illus- 
trated in  Figs.  80  and  81.  Note  the  vigor  and  pro- 
ductivity. 


1924} 


CORN  BOOT,  STALK,  AND  EAR  EOT  DISEASES 


463 


FIG.  85. — ANOTHER  GOOD  CROSS 

Note  the  low  stalks  and  large  ears.  These  plants 
represent  a  first-generation  cross  between  the  strain 
illustrated  in  Fig.  80  and  an  inbred  strain  of  the 
Illinois  High  Yield. 


464 


BULLETIN   No.   255 


[August, 


On  the  other  hand,  it  often  happens  that  little  is  gained  by  crossing 
certain  selfed  lines.  Such  a  result  may  be  due  to  close  relationship  or 
to  the  fact  that,  even  without  close  relationship,  the  lines  happen  to 
resemble  each  other  too  closely  in  their  genetic  constitution.  The 
genetic  factors  for  yield  and  vigor  being  largely  the  same  in  both 
parents,  crossing  accomplishes  little  more  than  self-fertilization.  Also, 
some  F  1  's  are  vegetatively  vigorous,  but  are  susceptible  to  diseases 
and  are  low  yielders  of  seed. 

The  problem  of  successfully  crossing  pure  lines  resolves  itself  into 
a  choice  of  lines  to  use  as  parents.  Without  more  information,  it  is 
possible  to  point  out,  in  only  a  general  way,  the  characteristics  on 
which  such  a  selection  should  be  based:  namely,  the  parental  lines 
should  be  themselves  fair  producers  of  grain  in  order  that  they  may  be 
multiplied  rapidly  for  crossing  on  a  large  scale ;  they  should  have  the 
same  grain  color  so  that  grain  produced  by  the  hybrid  will  be  uniform 
in  color  (this,  however,  is  not  an  important  consideration  if  the  grain 
is  to  be  used  for  feeding  live  stock)  ;  and  finally  they  should  exhibit, 
so  far  as  possible,  the  desirable  plant  and  ear  characteristics  described 
in  the  first  part  of  this  section. 

Obviously,  the  best  results  will  be  secured  from  the  use  of  single 
crosses  if  they  are  made  anew  each  year.  The  following  plan  may  be 
suggested  for  producing  the  hybrid  seed  in  quantity.  Let  one  selfed 
line  be  designated  by  A,  the  other  by  B.  Two  fields  are  required, 
Field  I  and  Field  II,  sufficiently  isolated  from  each  other  to  prevent 
cross-pollination.  It  is  immaterial  whether  they  are  of  the  same  size 
or  not.  In  these  fields,  strains  A  and  B  are  planted  according  to  the 
following  diagram : 


FIELD  I 


FIELD  E 


I 


I  I 


11 


I     2.34StrttM 


10 


In  Field  I,  two  rows  of  strain  A  alternate  with  four  rows  of  strain  B. 
All  rows  of  strain  B  are  detasseled,  and  being  pollinated  by  A  pollen 


J924]  CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES  465 

produce  hybrid  seed  only.  Rows  planted  to  strain  A  produce  pure  seed 
of  A.  In  Field  II,  two  rows  of  strain  B  alternate  with  four  rows  of 
strain  A.  All  rows  of  strain  A  are  detasseled,  and  being  pollinated  by 
B  pollen  produce  hybrid  seed  only.  Rows  planted  to  strain  B  produce 
pure  seed  of  B.  Thus,  this  plan  provides  for  the  production  of  hybrid 
seed  each  year,  as  well  as  the  production  of  pure  seed  of  the  two 
parental  lines.  Also,  hybrid  seed  is  produced  on  two-thirds  of  the  total 
acreage  while  only  one-third  is  devoted  to  continuing  the  strains. 

DOUBLE  CROSSES 

Since  it  is  improbable  that  all  desirable  qualities  will  be  found  in 
any  two  lines,  it  would  appear  that  the  combination  of  several  lines 
would  produce  a  hybrid  type  superior  to  any  single  cross  that  could 
be  made.  That  this  result  may  reasonably  be  expected  in  certain  cases 
is  indicated  by  the  work  of  Jones54  on  double  crosses. 

Let  A,  B,  C,  and  D  represent  separate  lines  which  have  been 
rendered  practically  pure  by  inbreeding,  and  which  possess  individu- 
ally one  or  more  characters  of  outstanding  importance,  such  as  a 
strong  root  system  or  resistance  to  root  and  stalk  rots.  These  strains 
would  be  combined  into  single  crosses  first  and  then  into  a  double 
cross  according  to  the  following  diagram: 

Strains \        B  C        D 

Single  crosses A  X  B  C  x  D 

Double  cross (A  X  B)  X  (C  X  D) 

If  the  parent  strains  are  pure,  the  plants  of  either  single  cross 
would  show  marked  uniformity  because  they  would  all  have  the  same 
genetic  constitution.  Variations  among  them  would  be  due  to  environ- 
mental conditions.  This  cannot  be  said  of  the  double  cross,  however. 
While  in  one  sense  it  can  be  considered  a  first-generation  hybrid,  in 
another  sense  it  represents,  in  its  relation  to  the  previous  crossing,  a 
second-generation  hybrid.  It  will  show,  therefore,  considerable  varia- 
tion because  it  consists  of  plants  which  differ  genetically.  Indeed,  so 
great  is  the  possible  number  of  factors  in  which  the  parent  lines  may 
differ,  that  it  is  not  far  from  the  truth  to  state  that  scarcely  any  two 
plants  would  have  exactly  the  same  genetic  constitution.  This  is  be- 
lieved to  be  a  desirable  situation.  Numerous  types,  with  varying 
capacities  for  utilizing  the  plant  food  and  moisture  at  their  disposal, 
often  will  produce  better  collectively  than  if  the  population  consisted 
of  but  one  type,  all  the  plants  of  which  were  uniform  in  their  capacity 
for  development.  It  is  likely,  also,  in  view  of  the  large  amount  of 
crossing  that  is  continually  taking  place  under  field  conditions,  that 
the  population  might  be  continued  for  a  few  years,  by  careful  selec- 
tion, without  any  very  noticeable  decrease  in  yield. 


466 


BULLETIN   No.   255 


W24] 


CORN  ROOT,  STALK,  AND  EAR  ROT  DISEASES 


407 


FIG.  86. — EARS  PRODUCED  IN  THE  PURE-LINE  METHOD  OF  CORN  BREEDING 
Representative  ears  of  inbred  strain  A   (upper  left),  inbred  strain  B   (lower 
left),  and  the  single  cross  of  A  X  B   (upper  right).     This  single  cross  yielded  at 
the  rate  of  117.2  bushels  per  acre  (Table  36).     (The  ears  were  photographed  on 
1-inch  mesh  screen.)     Bloomington,  1923. 

The  pure-line  method  of  corn  breeding  is  believed  to  have  a  distinct  place 
in  this  program  because  of  its  possibilities.  It  is  fundamentally  sound  in  theory. 
The  practical  benefits  from  its  use  are,  in  the  main,  still  to  be  realized.  Tho 
many  problems  remain  to  be  worked  out  in  regard  to  the  utilization  of  inbred 
and  hybrid  strains,  it  is  felt  that  enough  is  already  known  to  justify  considerable 
confidence  in  the  importance  and  ultimate  value  of  the  method  in  corn  production. 


MULTIPLE    CROSSES 

Since  good  results  have  been  obtained  by  combining  four  selfed 
lines  into  a  double  cross,  probably  still  better  results  may  be  secured 
by  combining  many  more  such  lines  into  what  might  be  called  a 
multiple  cross.  This  is  only  suggestive,  as  no  experimental  data  are 
available  on  this  point.  However,  it  would  seem  that  the  more  lines 
there  are  entering  into  the  cross,  the  better,  because  the  result  would 
be  greater  genetic  diversity  and  variation,  and  consequently  better 
response  to  seasonal,  soil,  and  other  conditions.  Furthermore,  the 
general  superiority  of  the  multiple  cross  could  probably  be  continued 


468  BULLETIN   No.   255  [August, 

In  the  practical  utilization  of  double  or  multiple  crosses,  the  Experi- 
ment Station  or  the  professional  plant  breeder  must  cooperate  with  the 
corn  grower,  the  former  furnishing  the  double  or  multiple-crossed  seed, 
the  latter  continuing  it  by  selection.  After  a  time  it  may  become 
necessary  for  the  grower  to  return  to  the  original  supply  for  his 
hybrid  seed  because  in  spite  of  careful  selection  the  proportion  of 
plants  possessing  the  genetic  constitution  of  the  original  hybrids  is 
likely  gradually  to  decrease,  and  the  yield  will  accordingly  be  reduced. 
The  general  average  yield  of  the  hybrid  seed  in  this  period,  however, 
would  probably  be  enough  in  excess  of  that  given  by  ordinary  varie- 
ties to  warrants  its  use. 

The  method  proposed  above  would  have  several  advantages  from 
the  practical  point  of  view.  It  would  permit  a  fairly  rapid  increase  of 
seed  for  general  distribution.  It  would  not  be  necessary  for  the  seed- 
corn  producer  or  corn  grower  to  maintain  isolated  seed  plots.  There 
would  be  little  danger,  for  some  time  at  least,  of  securing  uniformity  at 
the  sacrifice  of  productiveness  because  of  the  hybrid  origin  of  the  seed 
stock  and  the  consequent  recurrence  of  varying  hereditary  combina- 
tions. And  finally,  abundant  material  would  be  at  hand  at  all  times 
for  selection. 

PROBABLE  USES  OF  THE  TWO  METHODS  OF  CORN 
IMPROVEMENT 

The  pure-line  method  is  of  incalculable  value  to  the  investigator. 
It  provides  him  with  a  tool  by  means  of  which  he  can  resolve  the  corn 
crop  into  its  component  elements  and  analyze  them,  saving  what 
appears  useful  and  discarding  the  rest.  For  example,  he  can  isolate 
and  recombine  the  genetic  factors  which  affect  root  development  and 
thus  build  up  a  type  with  a  superior  root  system  particularly  adapted 
to  drouth  conditions. 

Self-fertilization  may  be  likened  to  the  analytical  method  employed 
by  the  chemist.  It  is  a  breaking  down  process  according  to  which  the 
investigator  takes  the  corn  crop  as  Nature  has  given  it  to  him  and  deter- 
mines of  what  it  is  made  up.  Then  he  takes  the  parts  he  wants  and 
builds  up,  synthetically,  the  particular  type  desired,  by  hybridization. 
Hence,  analysis  and  synthesis  are  the  keynotes  of  this  method. 

For  a  considerable  time,  probably,  the  method  of  careful  seed 
selections  will  be  largely  used  by  the  majority  of  seed  producers  and 
farmers  in  improving  their  corn.  This  must  necessarily  be  the  case, 
because  of  the  length  of  time  required  to  obtain  tested  lines  for  use  in 
producing  hybrid  seed.  However,  as  the  superiority  of  hybrid  seed 
becomes  more  firmly  established,  and  information  concerning  it  spreads 
among  corn  growers,  there  will  result  an  increased  demand  for  it.  To 


1984]  CORN  ROOT,  STALK,  AND  EAR  EOT  DISEASES  469 

meet  this  demand,  hybrid  seed  production  will  have  to  be  put  on  a 
commercial  basis.  While  practical  difficulties  which  have  always  been 
urged  against  this  method  are  not  believed  to  be  insurmountable,  the 
utilization  of  hybrid  seed  in  corn  production  will  be  most  efficient  only 
when  there  is  complete  cooperation  between  the  Experiment  Station, 
the  professional  plant  breeder,  the  seed  producer,  and  the  corn  grower 


470  BULLETIN   No.   255  [August, 

SUMMARY 

On  the  basis  of  the  data  reported  in  this  bulletin,  as  well  as 
of  observations  made  thruout  Illinois  for  a  period  of  years,  the 
authors  feel  that  where  inferior  and  infected  seed  is  used,  losses  to 
the  corn  crop  from  disease,  including  smut  and  rust,  can  very  con- 
servatively be  placed  at  20  percent. 

An  adequate  understanding  ef  the  causes  of  the  corn  root,  stalk, 
and  ear  rot  diseases,  and  variations  in  susceptibility  of  different  strains 
of  corn  to  these  diseases,  can  be  obtained  only  by  a  consideration  of 
all  the  influencing  factors. 

Planting  of  Diplodia-infected  and  Gibberella-infected  seed  always 
has  resulted  in  a  reduced  stand,  many  blighted  and  weak  plants,  and 
a  lowered  vigor  and  vitality  of  those  plants  which  survive. 

Good  seed  corn  of  strong  vitality  and  free  from  infection  will 
grow  under  a  wider  range  of  temperature  and  moisture  and  can  be 
planted  with  safety  much  earlier  than  infected  seed  or  seed  affected 
with  scutellum  rot. 

In  general  appearance,  good  seed  ears  are  mid-sized,  heavy  in 
weight,  bright  in  luster,  moderately  horny  to  horny  in  kernel  com- 
position, and  moderately  smooth  to  smooth  in  indentation.  Shank 
attachments  are  bright  or  only  slightly  discolored,  and  in  no  case  is 
there  evidence  of  rotting  of  the  tissues  at  the  butt  of  the  cob.  Tips 
of  the  ears  have  been  covered  by  the  husks  or  only  slightly  exposed. 
Starchy  seed,  regardless  of  its  germination  record,  is  very  likely  to 
produce  corn  more  or  less  susceptible  to  the  attack  of  certain  para- 
sitic fungi  and  to  injury  from  unfavorable  weather  or  soil  conditions. 

An  important  consideration  in  corn  production  is  disease  re- 
sistance, a  condition  which,  up  to  the  present  time,  the  authors  have 
not  found  associated  with  starchy  seed  or  infected  horny  seed,  but 
rather  generally  associated  with  seed  from  apparently  healthy  plants 
that  shows  vigor  and  freedom  from  disease  on  the  germinator  and 
that  is  horny  in  composition. 

Nearly  disease-free  seed  of  a  susceptible  strain  or  selection  may 
yield  even  less  than  moderately  diseased  seed  selected  from  apparently 
good  plants  of  a  highly  resistant  strain,  thus  suggesting  the  advantage 
of  selecting  seed  in  the  field  from  standing  plants  and  the  value  of 
the  germination  test  in  securing  seed  which  will  produce  plants  more 
highly  resistant. 

Some  strains  of  corn  are  so  susceptible  to  disease  and  so  deficient 
in  those  qualities  which  make  for  high  yield  of  sound  corn  that 
neither  physical  nor  germinator  selection  can  effect  any  improvement 
in  either  quality  or  quantity  of  the  crop. 


CORN  BOOT,  STALK,  AND  EAR  ROT  DISEASES  471 

The  relative  degree  of  resistance  and  susceptibility  possessed  by 
different  strains  and  selections  of  corn  cannot  always  be  determined 
accurately  by  plantings  on  one  date  in  one  locality  involving  only 
one  set  of  environmental  factors. 

The  greatest  improvement  in  resistance  and  productivity  may  be 
expected  to  accrue,  not  from  physical  selection  of  seed  ears  alone,  but 
also  from  the  continuous  practice  of  plant  selection  and  germintor 
selection,  always  beginning  with  a  strain  which  has  possibilities  for 
improvement. 

Altho  variations  in  disease  resistance  are  greater  in  open-polli- 
nated corn  than  in  uniform  inbred  strains,  yet  there  are  open-polli- 
nated strains  that  are  highly  resistant  to  certain  of  the  corn  rot 
diseases.  This  resistance  can  be  maintained  by  constant  selection. 
Complete  resistance  or  immunity  to  a  majority  of  the  corn  rot  dis- 
eases seems  possible  only  by  the  recombination  of  two  or  more  highly 
resistant  and  reasonably  productive  inbred  strains  which  nick  to- 
gether in  a  compatible  way. 

The  data  that  have  been  presented  on  disease  resistance  and  sus- 
ceptibility furnish  strong  arguments  for  the  use  of  resistant  strains 
of  corn  and  of  approved  rotations  in  which  there  is  a  more  liberal 
use  of  legumes. 

Data  from  rotation  experiments  up  to  the  present  time  indicate 
that  crop  rotation  is  as  important  a  factor  in  determining  yield  of 
corn  as  are  soil  treatments. 


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,  if 


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